Generally, the one is right who builds his argument on verifiable facts coming from trustworthy sources, or at least tries to as best as possible. There are police statistics about crime rates. In Germany for example, crime is actually going down. It’s very likely that Harris is right and Trump is not. This is usually the case, without even looking at anything specific. Trump lies and does baseless/unverifiable claims about pretty much anything, all the time. His followers then think he’s somehow right because he’s anti-establishment or they think that it’s all a giant conspiracy and Trump is the only one who knows the truth, again without any kind of verifiable facts behind it. This can then spiral into pure fact-free lunacy or high fantasy thinking, or cult-like thinking.

That crime is going down, is of course a fact that doesn’t fit at all into the right-wing world view or rhetoric of blaming and demonizing immigrants. So they usually then claim that those facts come from untrustworthy sources or are generally fake news or whatever, again without any verifiable evidence. Because they don’t want facts but easy solutions to complex problems, like minorities to blame for whatever problems they currently believe in. If they radicalize themselves enough, and this can happen fast on today’s internet within their own echo chambers, they might become so far removed that they become lunatic and/or violent, and then they become dangerous. Fascism is very similar to a cult.