If they are requested by local authority and legit required to keep order they're not a problem. When they are sent by Trump as a fuck you for his own political benefit and they are oppressing peaceful protesters that's tyranny. Snatching up people without cause or explanation, detaining them without cause, beating people for no reason, denying their constitutional right to counsel is tyranny.
Many Americans support the Second Amendment, the two reasons I always hear are self-defense and because they believe an armed citizenry is a defense against tyranny. That couple in St. Louis weren't being threatened at all and yet many cheered when they waved their guns around threatening the peaceful march coming past their home on their way to somewhere else. So I'm sure they wouldn't have any objection when this tyranny is met with armed resistance. Surely they would not be such hypocrites.