To some extent I agree with you, but IMO it's a mistake to think that (most of the time) people call Trump supporters these things simply because they support Trump, but mostly rather because they've already attempted to engage with some of his supporters and that is their feeling about that person after having done so. For example, in another thread, a Trump supporter denounced another person for 'promoting murder', then refused to meaningfully address my counterpoint that he gave Trump the greatest possible endorsement despite admitting he disagreed with Trump also 'promoting murder' yet felt it was appropriate to call someone else out for the same behaviour.
I think a problem is that many Trump supporters see Trump getting away with very problematic behaviour and then when they repeat that behaviour themselves, they get antsy when people call them out for it, and while I agree that say calling someone a racist POS does exacerbate the situation, if it was a factually appropriate descriptor then it's simply calling a spade a spade.
Previously I've read about situations where a person with extreme viewpoints has been convinced of the errors of their ways through calm and collected discourse, and I'd love to achieve that kind of objective myself with such people, the big question is how to identify such people. Many people are simply wilfully ignorant however, and I think spending time trying to civilly discourse with such people to achieve a productive end is simply a waste of time. "You can lead a horse to water but you cannot make it drink".