I don't get it, frankly. I read Tracy's FB news. I haven't done a census, but she likely has slightly more conservative than liberal friends, among those that are political at all. But I don't see political comments inserted by conservatives in the general flow of things, apropos of nothing. I don't see many from liberals either, but the few that I do see are always from liberals, and always of the entirely social variety, rather sneering at how hateful/stupid/angry a particular conservative, or perhaps Republicans in general, are.
Are people just unaware that friends who disagree with their politics are "present," and may find such things insulting? I am not sure if it is merely an insensitivity, or a communication of enforcement "My friends have these politics. I will cut you publicly if you say otherwise?" Who wants a friend like that?
I have seen the same in conversation, of course. I imagine everyone has. It is most common in a situation where the speaker believes that everyone present must of course share their views on the subject. I have certainly heard conservatives do it, not so much at the churches I have attended as at the schools my children attended. One could hear such assumptions, a "my how terrible those people out there are" attitude on a variety of subjects, political, social, religious - not only in conversation while slicing tomatoes or waiting for soccer teams to return, but from the speakers at events. I found it offensive then, also. I wondered with that group as well if there were something worse than insensitivity present, a declaration of "if you want to be one of us you have to believe this."
I hear it all the time at work, enough so that it seems like background now. The same half-dozen liberals make hateful comments all the time, and an overlapping half-dozen will make anti-Christian statements. Sometimes a new voice will be heard from, or the context will be different, and it will catch my resentment unaware.
I can hardly be accused of not wanting to discuss politics and religion. But there is a social grace to it, a testing of whether a person wants the topic to come in. It's just rude to stand in the lobby and complain that Obama is being dishonest or foolish. It's rude even in the context of someone making a general comment about a political issue, such as the budget deal. You don't just launch with a pre-emptive strike that you think the people you disagree with are stupid or evil, for the simple reason that the person you are speaking to might be one of them, or one might be overhearing.
Maybe this is a New England thing, where liberals believe they own the culture and have the right to defend it. Maybe the opposite happens in, oh, Oklahoma or something. But from this vantage point, it is a rudeness far more common among liberals.