“By those standard you couldn’t vote for Hillary either”
For people of conscience who participate in the process, backing Clinton once she’d become the nominee was merely a matter of selecting the inarguably lesser evil. But that’s still an evil, and you’re basically correct.
“Moralizing your opposition to him will not convince anyone to see your point of view.”
You say that as if it’s something one must proactively do, as if there was even any other choice in the matter. No moral argument exists for holding any view of Trump other than contempt and revulsion. Supporting Trump necessarily involves abandoning nearly every standard I outlined earlier. That doesn’t mean one can’t do it anyway — sometimes even a bastard is useful. It’s just important to keep in mind what that entails.
Convincing people who are that lost and seemingly hopeless is a different matter, and the truth — and the good news — is that most of them aren’t hopeless. Trump’s hardcore support amounts to a minority of even his own minority party.