There’s never a line with this kind of thing.
We have a lot of popular fiction where the Bad Guy is a Trump-like figure, and at some point he hits The Line and then like his brutal-but-noble second-in-command turns on him. Return of the frigging Jedi is literally that trope. But that trope is part of the fiction: just like we wish Superman or Batman (or the Punisher . . .) were “real”, we also wish that “the line” was real. We write it into our fiction because it doesn’t play out in real life, and just like an immaculately-moral hero from the stars won’t save us in real life, likewise there will be no “too much” for the MAGA cult. Sure, some or even many will fall off as things get more extreme, but the “true believers” will double-down (or feel forced to double-down). This vile gangster literally said he could shoot someone in public without consequences, BEFORE he was ever voted in. This is the game that we are stuck in.
This only ends when he is *gone*.