The moral line he crossed is that he induced people to physically attack the democratic institutions that he swore an oath to protect. Even if accidental, this is a monumental failing.

I like the word "incitement" because the meaning precisely fits what he did. If you like a different word with sufficiently close meaning, maybe because you don't like the legal connotations of "incitement", sure, I'm happy to use that word instead while talking with anyone who dislikes the connotations.

Doesn't change the reality, or the morality.

Most Presidents don't seem to have had a problem understanding this. Words have great power when spoken with this much authority. Indeed, nobody on the right seems to have any trouble understanding the gravity of the office when Biden says something ill-advised.

Bringing up other cases where the U.S. has engaged in morally deficient policy or other politicians have engaged in morally deficient behavior in no way detracts from Trump's moral failings here.

That's not how morals work. When things are morally wrong, they're just plain wrong. That's part of what we mean by things being morally wrong.