I feel there is very little we can do individually to change people's minds or turn them away from fascism, or even to get them to stop turning their own brains into soup, but you can still show them there are consequences to their actions.
Telling my own friends / relations what I think of them and cutting ties with them has done nothing to bring them back in line with normal human values, but at least I am not burdened with the guilt of my association, and maybe one day enough people will cut them off that the loneliness gets to them and they begin to re-evaluate their lives.
It is literally the least I can do. Any sadness I felt was heartbreak that they could be so shitty to begin with.
I think it's a useful way to tell whether or not people actually care. When it comes down to the wire of "bye bye seeya again never", a person who actually cares but has bad ideas will at least make change-like noises when confronted with never seeing someone again. Actual bastards will fall back on more hateful garbage, I find.