OK, so while being "very left-leaning" you walked in a nest of conservatives, so you get points for bravery ;)
Note: I'm gonna use "leftie" and "rightie" because in my country "libéral" means "free-market capitalist" so it gets confusing versus "liberal," etc. I'm not using them as slurs, just abbreviations.
I really didn't like the fact that they moved on; I felt like I was being ignored.
Well, you did make a few mistakes.
Many Trump supporters would view a Hillary supporter as, at best, mildly insane, and at worst a commie. This works both ways, of course, as the lefties are prompt to slap labels like "deplorable racist sexist nazi" on anyone who disagrees with them.
This is not conducive to rational communication. In fact, this whole event was going to be an uphill struggle right from the start. I guess you missed this, perhaps due to the fact the lefties are very vocal about their opinions on the righties, so everyone pretty much knows what they think, but the righties tend to be much quieter, so you might not have known, but I can assure you it's like that. Can you confirm?
I find it quite funny having to explain the Overton Window to a leftist. This window is the range of acceptable speech in a given environment. Anything outside of this window will shock people and earn you a blank stare (as you experienced). Too far out and you might start a fight.
So, I presume you didn't listen long enough to place these guys on the political spectrum (there are many such models, I find this one lacks a PC axis) and get a workable estimate of their Overton window. Without this, you couldn't foresee their reaction to what you'd say, nor choose the right words.
If something is smack in the middle of the window (ie, it's the consensus) then you can word it as a correction. Further away from the center, it should be worded as a suggestion. Even further, as a hypothesis.
It doesn't matter if it's true or not, btw. This is only about how others will react to it. If you think it's true and word it in a way that is badly received, you might very well persuade others that it's not true!
Which leads us to...
Come on, you just entered the dungeon and you went straight for the boss fight.
You could have picked a very minor point, something that they don't really care about, your choice of topic, although anything is a polarizing issue these days.
So, first thing is to get rid of the "hysterical liberal" label that you automatically acquired when stepping into this nest of conservatives. You do this by starting with little things, not too polarizing topics... have an adult conversation about it, and above all... lose the self-righteous, "i'm gonna correct you" attitude:
So I spoke up. I don't remember exactly what I said, but I think it was something along the lines of "Oh, they have software that can do that. It's all automated." I remember getting a blank stare in response
You really sound like James Damore being surprised that his memo got him fired. When I downloaded the memo and read it, I immediately thought "man, he's soooo fired." I wondered how someone who seems to be very smart could make such a blunder. I guess he never heard of the Overton window... An interesting experiment would be for you to read said memo (not the journalists' reports) and try to understand why he didn't.
If these were the words you used, again no surprises here.
You could have said "I'm not sure, but it's the damn FBI, don't they have software and tools to sort through this? It can't be the first time they seize tons of emails. This sounds weird, what do you think?"
Or "Mmm, 10 seconds to glance at an email, 6 hours a day because headaches, 8 days, that's about 17000 emails per guy, you'd need 50 people, I mean it's the FBI, that could be a national security issue, I'd certainly hope they can do that, don't you think?"
In both cases: wrap it in maybe's, sound like you're reasoning instead of lecturing, like you're asking for their help to solve a problem, sugarcoat a little, and end with an open question.
Then, if they admit Trump may not have been telling the truth... (He's a politician, btw, so yes he's gonna lie and spout rhetoric, no surprises here).
Come on. You can't possibly expect to say "But! Trump lied!" and be taken seriously, while supporting a Clinton.
Here, we all know our politicians are lying self-serving bastards. Culture shock, I guess! Anyone raving about a candidate will usually earn "you really believe this shit he said?" and the usual reply is "well, no, but he's less worse than the others, so... okay..."
"Well, maybe he was in a lying contest with Hillary! Politicians..."
This wraps up in just a few words that you acknowledge that not all conservatives love Trump, that you feel the same about your candidate, like "Well what could I do, there were no other democrats to vote for!"
If you're lucky someone will say "yeah, same here".
Now I'm gonna tell you the truth about this quote:
You can't review 650,000 new emails in eight days. You can't do it, folks," Trump said, adding, "Hillary Clinton is guilty. She knows it, the FBI knows it, the people know it, and now it's up to the American people to deliver justice at the ballot box on November 8.
I know it's a lie. But it's excellent rhetorics, and it got Trump elected. So he was right in saying it.
Elections are not won by being nice...
I knew I was upset and decided not to press the issue.
Don't debate politics while upset. If your opponent is any good, they'll turn your own feelings against you and make you dig your own hole. If you get upset enough, you might even lose your wits and do it on your own...
You made a bad first impression. Not pressing the issue was a wise decision.
Now, I'll go on a tangent: I followed this election with lots of attention from the other side of the atlantic, due to the stakes. This is a bit fuzzy now, since I'm writing from memory, but that'll do. When Comey happened, there was quite a bit of debate on conservative websites about why. He seemed to be a Clinton supporter at first. So, why did he sink Clinton? People wondered if he'd been blackmailed or pressured. The whole business smelled very suspicious. Also, at the time it happened, the media seemed to lessen their previously extreme pro-Clinton bias. This was really noticeable. Some tinfoils postulated that the "deep state" had dropped support for Hillary due to her being insane, out of control, too corrupt, a vocal supporter of war with Russia, and possibly the spawn of Satan, in no specific order. After the election, it came apparent that many media outlets also fudged the polls. So the polls were also fake. But since I'm french, I'd be surprised anyone would be surprised about fake polls. Our pollsters have been caught red-handed numerous times...
So... IMO, it is likely that both your conservative ex-buddies and you are wrong, no-one will know the gory truth of who messed with the elections. I'd bet that lots of shady stuff happened. Both sides probably cheated, ballot stuffing was reported, etc.
So to close the "ask a conservative if Comey sunk Clinton" tangent: I have no idea, most likely the truth will never come out, debating about it seems futile.
And I really don't like it when people disagree with me, not about issues, but about basic facts about events.
I disagree with you on the facts: I think the facts are unknown, buried too deep under too many lies and potential scandals.
It's like dark matter: you can see the galaxies and celestial bodies have unexplained orbital velocities, so there must be an underlying reason, but what is it?... Haven't found it yet!
This means you really picked the worst possible topic: in order to win, you'd have to convince them that they're wrong, but also admit that you're wrong...
While I don't necessarily expect people to agree with me on everything, I appreciate it when I'm heard out.
Well, to wrap this up I'm gonna explain how to get along with conservatives:
(Very) broadly speaking, there are two kinds of lefties: libertarians and authoritarians. I get along just fine with the first because they're usually very open to debate. In fact I enjoy talking with them. They're more the classical liberals. An example would be Jordan Peterson (he's kinda my liberal crush).
As for the authoritarians, egalitarians, the PC/SJW crowd, now this is a different can of worms. Since most of the media, journalists etc belong to this category, conservatives are constantly bombarded with messages telling them they're wrong, evil, etc, also facts are systematically ignored... a bit like what you experienced, I sympathized with you not liking the experience.
Thus, anyone leaning slightly to the right develops a very strong bullshit filter. If they characterize you as hysterical liberal, they will simply tune you out, thinking "Not again! Go away!"
Consider TheEnvironmentalist's response, who helpfully provides a perfect example of this. He chooses to frame conservatism as a kind of a mental illness or something, then frames the righties as clueless temperamental children who will throw a tantrum if you disagree.
This misses the point: they simply ignored you because you opted to posture as the stereotypical liberal taking the moral high ground and lecturing them. And they've had enough of this. So you got kicked out.