I wish I could think of an example, but I generally figure people can relate any story to a similar experience, so the idea of limiting conversation like that is foreign to me and I wouldn't even notice that I'm not doing it.
But thinking about this later, it occured to me that there's a hole in the "I'm too nice to realize that I respect people" theory. Or, at least an alternate theory presented itself:
Maybe I don't notice that the conversation has veered from someone's accepted range of interests because I'm talking about what I want to talk about, and genuinely don't care what anyone else is interested in.
And that's plausible. After all, what is "selfish" if not "kind of like self"? Self is what Selfish aspires to be. When I see children not sharing their toys, I grumble "amateurs!" under my breath and then refuse to give them the time of day. Sure, I could offer some pointers, bring them up to my level. But it's not about them.
So... Brownie points for insensitivity!
I can live with that.