What about the KIA EV6 or the Mustang Mach-E? Both are great alternatives to the Model 3.

Ish, we can't assume that everyone, or even most people, who own a Tesla support a CEO's actions, know about his actions, or even care. People just want to get the best product that works for them, and at this time, the only direct competitor to the Model 3 is the Ioniq 6 (worse value). The Model Y has some competitors, with the direct ones being the Mach E, Equinox EV, and Ioniq 5, but it's recently the bestselling vehicle in the US and is extremely popular elsewhere. Assuming that all of those people support "neo-Nazis" is extremely ignorant, and you're directly contributing to the major culture problem going on where people feel they act a certain way just to not get harassed and insulted.

If you are driving a Cybertruck, or any Tesla for that matter, magnet intolerance is the least of your concerns. Looking like a MAGA douchebag and supporting neo-Nazis I'd think would be more of a concern.