Given that police routinely assault peaceful demonstrators, journalists and random bystanders, wearing body armor if you might be anywhere near a protest (whether as a protestor or just because you live, work or transit through such an area) seems like common sense.
Body armor is the most obviously genuine "self defense" item a person could have. A gun, knife or pepper spray might be used for self defense or attack, but armor is purely defensive.
Your whole argument makes no sense. You just hate liberals and are happy to have your perceived enemy behind bars, no matter what degree of authoritarian police state it requires to achieve that end.