As I said in my original comment:
As usual, the anti-war activists are going to be labeled "enemies of the state," foreign actors, etc. It's already happening to BreakThrough News, the DSA, PSL, etc.
It's easy to simply call people "pro-Putinists" and then make lists, crack down on them, repress them, etc. Calling anti-system agitators "foreign agents" or "foreign influenced" is a time-tested tool of fascism.