Trump's supporters like him because he's saying these things, not despite them. The Niemöller paraphrase sounds ridiculously melodramatic to people who don't support Trump.
Frankly, there's a big chunk of this country that has wanted to go after Muslims, illegal immigrants, and the press for a long time. Confirming that Trump has it out for those groups just makes Trump more attractive as a candidate to those people, not less attractive.
You're right that you can't fix stupid with his supporters but his numbers can be contained with ads like this