GP said they don't live in the US, it's possible English isn't even their first language. If they are a non-native speaker and just made a translation/wording mistake, you might feel like a pretty big asshole twisting that to call them a fascist (which word btw, is pretty overloaded and has become essentially meaningless to a large number of people).
It's also quite possible they mean "Americans" in a general sense in that the Marines are not being turned loose on the American public. They are being focused on the rioters specifically.
Obligatory self-declaration since you and many others will probably jump to conclusions about my opinion (as for whatever reason, we seem incapable of nuance even to the point of understanding that not everything in life is completely black or white), even though I've said nothing of it until now: I think Trump's actions are grotesque, authoritarian, and fascist, and it really pisses me off.
I have neither seen nor heard anything that would lead me to believe most of the protesters are non-citizens or non-resident. You are not providing any evidence, just conveniently excusing this overreach by the executive branch by ignoring the rights of the protesters with a facile lie.
I really don't have to. You're arguing your talking points, but not to any verifiable reality. You should have said "if they're all citizens, they are american" which is the same thing you're saying, but without the implication you're adding that those people protesting have no rights. So you should probably say what you mean instead of this mealy-mouthed weaseling you're doing.