Well, I can only guess..
Biggest factor is probably that many people think I'm not interested in them. I assume that my way of ending conversations is weird. Like, that I turn away too soon or so. But I'm not sure about it.
Then, I just have different interests and opinions than many others. A very common small talk topic is football/soccer (Germany, you know..), and there's no way I could pretend to be interested in that. I'd rather risk people don't want to talk to me than acting as if I'd like to talk about stupid stuff. They just aren't the right people for me to spend time with, anyway.
But several times, I drove good friends away from me, and that's very sad. When I look back, I guess, I was too persistent about an opinion that I discussed with them. I don't talk too much about my obsessions (at least I think so!), because I've already known for a long time most people don't want to hear about it, instead it's more about specific political opinions that are very important to me.
And I sometimes think everybody must come to the same conclusions when they have some background knowledge about a political topic. So I can not really understand why a person I like and appreciate in everything else, would have an opinion that is "wrong" from my point of view.
Oh, wow, it's therapeutical to write that down here... Now I see why others have a problem with my behaviour.