First, it seems to take for granted that the ideology you’re opposing has lots of people behind it, or at least has the potential to get lots of people behind it. But at this point in society, advocating for, say, the return of slavery is so far outside the realm of acceptance that I don’t see much of a gender of it spreading even if its supporters proselytized openly.

… my guy have you not been paying attention

Slavery was only totally abolished in the 1940s with the end of peonage in Texas. People today still openly defend slavery. Florida’s new curriculum for public schools includes the idea that slavery was good for Black people because it ‘taught them valuable skills’. De facto enslavement happens by the selective enforcement of unjust laws combined with targeting of minority and impoverished communities combined with for-profit prisons and subminimum wage in conditions that would be illegal anywhere else.

We’re not that far removed from actual, literal slavery, and it’s not a leap to believe that a fascist regime would joyfully reimplement it.

Second, I think it’s very dangerous to excuse violent behavior now on the grounds that you believe some unspecified person will inflict violence on you at an unspecified time in the future. In other words, you can’t attack someone just because you believe he and his buds are probably gonna jump you at some point later. Your purported ability to predict the future is not sufficient; that isn’t self-defense, and therefore it’s not a valid use of violence. This changes, of course, if the threat of violence is imminent and actually real at the time you attack them.

Again, that’s only valid within the context of a functioning state. That’s not a comment on morality, that’s a comment on civility (as in the quality of living in a civilized society).