There are certain statements you hear all the time in certain parts of the country, especially on a college campus. "How could anyone seriously support Donald Trump? They must be really stupid." I don't want to presume the intent behind statements like these. I think a lot of time they come from a place of seeking social acceptance. The person knows that he/she is talking to politically-like-minded individuals, so a "it's us versus them" statement like this makes them feel more secure and accepted in their group. It's the old saying that nothing quite bonds people like hating someone else. But this is not the caveman era. We all live in the same country. A very large, diverse country - I'll give it that. But still, hopefully, some sort of common set of values and culture bonds us that extends beyond language.
The problem with making these huge sweeping "People who support ___ are stupid, racist, mean, etc." is not just that it is disrespectful; it is that it is ineffective. And I get it, this is America, people have freedom of speech, etc. But we need to be strategic, about what we want to achieve, and how to actually achieve it. Words are powerful. Do you really think that , for example, a Donald Trump supporter, in hearing these statements, is going to think "Oh wow! That person is right. I am stupid! Guess I better not vote! Or, even, better, guess I should vote for Bernie instead! (again, this is just an example)." Come on. You don't need to be a psycology major to know that that is not actually how a person's thought process will unfold. It will probably be more like, "Wow, who does that person think he/she is to be calling me an idiot? Whatever, I don't care. I'm not listening to you. I am definitely going to stick to my guns."
So, the next time you think of making a statement like this, think twice. If you try arguing rationally, you may find that you don't need to be so loud for people to listen to you.