The red line for Trump's people unfortunately isn't doing anything bad. He could shoot a man on fifth avenue and not lose them. It would take him doing something which shows actual human decency and actually helps people. If he attempted to create "Trump-care" providing unconditional healthcare for all he would be impeached and out on his ass. God forbid if he were to recognize LGBTQ rights and acknowledge their legitimacy, that action would literally kill people from shock.