“Danger” is an evaluation of self-preservation for a given scenario. Whether the danger is deserved is a matter of justice, which is separate.
Nazis are “dangerous” even if they don’t do anything, because their support for the ideology of the Third Reich is only secondary in the evaluation. It is not so much that it’s dangerous to be around Nazis because they’ll long-knife you if you’re not a Blue Eyes White Aryan, it’s because non-Nazis will do it to you if you’re seen associating with Nazis – and non-Nazis far outnumber Nazis. Counterexample: no non-black has stopped supporting BLM even though they threaten about the same thing.
People like to say it’s actually because they believe Black Lives Matter or any number of other things. Perhaps they do. But if they do, then it’s also clear that they’ll change their opinion on homosexuals within ten years, fake news within four months, and additional funding to NASA within… well, people are calling for more space exploration funding all the time because They Fucking Love Science and Elon Musk Is Totally Tony Stark or Steve Jobs 2, and this article is fairly new, so “one second” probably is an overly generous estimate. “But there was new evidence” You’ll notice that people who learn and account for new things in any other subject will never say this line. “Well everyone changes their minds” So in the end, it really is about what the group thinks of you and not what you think of things.
No one ever thinks of BLM as dangerous because no one can touch BLM; “Treason doth never prosper: what’s the reason? Why, if it prosper, none dare call it treason“. They may think of going out in public with a mass of people is dangerous, or they may think that rioting is dangerous, but unless they’re a Nazi they don’t ascribe those to the named reason why people gathered.