The other day I was having dinner with some in-laws, and one of them made a claim which I fundamentally disagree with. I thought about asking him to explain his reasoning and tell him that I disagreed (in the hope of coming to a mutual understanding, not to start an argument), but then I thought: "Well, if I do that, even if I end up convincing him, it'll create an uncomfortable atmosphere for everyone else, and there's always the risk of it starting some argument." So I kept quiet.
Later I reflected on it, and thought about other times when I had interjected, and was usually met with an uncomfortable atmosphere (as if I was somehow being hostile), or even met with statements like "Nobody asked for your opinion." I think people often misunderstand and assume I'm trying to make them look stupid or otherwise start an argument, when really all I want is to understand why they think the way they do, and present some arguments of my own.
To provide a bit more context for the family dinner example: At one point, the conversation turned to human nature, and a younger (age 17) member of the family started talking about how humans are just animals, giving examples like survival instinct, sexual desires, etc. While I agree there are similarities between humans and animals (say, primates), I can also think of far more reasons why humans are not "just animals". The reason I didn't say anything is because I guess I didn't want to launch into what might be construed as hostile accusations and cause upset at a family dinner, and he is just a kid after all (I consider 17 to still be an adolescent) and still has a lot to learn.
To clarify further: Yes from a biological perspective humans are animals, but we were discussing it from a metaphysical perspective, i.e. saying that human nature is no different to the nature of a lesser primate, which I disagreed with.