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My background

Much like you, I'm a high functioning autistic person who mostly can "pass" as neurotypical. I've never had any meltdowns to the degree that you have, but I have spent a lot of time dealing with the social fallout from other side effects of autism that I do experience. I have found 2 things to be particularly helpful when dealing with this fallout.

  1. Explaining how autism affects me
  2. Having an advocate on my side

Explaining how autism affects me

As I explained in this answer

People have a tendency to expect certain social behaviors (such as the spouse of a family member coming to family functions). If someone knows that a person has autism (or some other diagnosis that causes them to have atypical social behaviors), it's been my experience that they will be more likely to alter their social expectations accordingly.

In your case, the behaviors that they expect are that you don't do all of the things that you've mentioned that your meltdowns cause you to do. You aren't going to be able to stop the meltdowns or the behaviors they cause, but you can help people understand why they happen. The typical way that I do that is by explaining how I am affected by autism. Because autism is such a wide spectrum, just telling people that I'm on the spectrum doesn't do much good because it gives little to no context of what challenges I actually face. Instead, I explain to people that my brain processes sensory information differently than most people, and I give analogies to illustrate what that is like (my personal favorite is to liken the brain to a circuit that can blow a fuse if it overstimulated).

A few years ago I wrote a blog post where I explained the challenges that I faced due to my autism. When I shared it, I had messages pouring in from friends, family, co-workers, acquaintances, etc... They all said basically the same thing.

Oh, I never knew that you had to deal with all that. I'll try to remember that in the future.

There are two ways to approach this. You can take a proactive approach and tell them before hand about your autism and the potential for meltdowns, or you can return after the meltdown is over and explain what happened. The proactive approach is more likely to be successful the closer you are to someone, so I would recommend only using it with close friends.

Having an advocate

Another really great solution to help with the social fallout is to have another person who can advocate for you. Ever since I posted the blog about my sensory issues with eating, I've been more proactive about telling people about my issues "in the moment" that I'm experiencing them. They end up being more receptive to the information because they get it at a time when it is useful for them to have it (i.e. when there is an action they can take or not take in order to help you). With your meltdowns you've pointed out that you are unable to communicate about your meltdowns in the moment, which is where having an advocate comes in.

Find a friend or two who you are frequently around and that you can trust to be your advocate. Explain the issues you have to them and ask that if they see you having a meltdown they help explain to the others around that you what is happening. This will give the others in the situation access to the information that they need in order to properly handle the situation.

In addition to the benefits of just getting the information out in a timely fashion, having an advocate makes others more likely to accept that your behaviors are genuine and not "playing the victim". The reason for this is the psychological phenomenon of social proof, which is

a psychological and social phenomenon wherein people copy the actions of others in an attempt to undertake behavior in a given situation.

Research has shown that the actions of a group have impacts on individuals within the group that last even once the individual has left the group.

When two or three individuals within a group give their judgments in the presence of each other (group situation) the whole group establishes a range and point of reference peculiar to the group. A norm once established in a group situation persists in an individual member even when he faces the same situation alone subsequently.

This study, and a others since have shown that the judgments that people make are influenced by the judgments of the group around them. Specifically, their judgments will be pulled towards whatever the collective judgment of the group is. By having your friends present the view that your meltdowns are 1) not a show and 2) socially acceptable, you will increase the likelihood that the others in the group will accept your meltdowns as an acceptable way for you to cope with stimuli beyond your control, thus decreasing the potential for social fallout.

I had this happen quite by accident a few years ago, but it turned out really well. I have a lot of sensory issues related to food. This has caused me some hassle throughout my life and I've had several people express the desire to avoid eating with me because of it. I had a coworker a few years ago who took it upon herself to educate some others about my sensory issues on my behalf. When she did this, coworkers who had previously been averse to getting lunch with me quickly became less so, which improved my relationships with them.