What's actually going on is a little bit more subtle, I think.
The people supporting him mostly don't know he's a rapist. They don't know he wants to throw his opponents in prison or kill them. All they see is this incredible opposition to him from people they know, and it just confuses them, because the news they consume doesn't tell them any of that. And so, they don't know what the big deal is, and so they just don't talk about it and plan to vote for Trump sort of quietly.
And, human nature being what it is, if it does come up in conversation, everyone talking to this guy assumes the underlying picture in everyone else's head is equal to the picture in their own, and so of course this person is already aware that Trump's a criminal rapist treasonous shitbag who's dumber than rocks, and just supports him anyway, and so they react with arguing and hostility instead of doing the much harder work of building a shared understanding and engaging in a dialogue that they know isn't going to resolve into anyone's mind changing on the first day.
It's easy to decide that someone's fully aware of the facts and they're just a huge piece of shit with how they reach judgements off the same facts you have, and you need to yell at them. That's rarely how it works though (although, sometimes, yes.) The much more difficult and more successful path is to understand where they're coming from and how they got to their wrong judgement, and try to work with them to help understand things better even if they're being hostile or what they currently think is wrong as hell.