Certainly, but if ~18 years of parenting wasn't enough guidance, what more can be done? At a certain point, they have to make the decision themselves to change, and if they won't there is little sense in trying to force it or provide further guidance. Further, this doesn't exactly sound like a small difference of opinion if they're calling their own kid "fascist", from the way it sounds it's probably a lot more than just wearing a red hat, this son might well have become a straight up unpleasant person to hang around and engage with; and I don't think one should be obliged to entertain fascists regardless of how you know them, they should be shunned, at best.