Don’t forget what happened at Ruby Ridge and Waco. I would not have thought that US Fed LEOs would be willing to do what they did, and with no remorse.
Most active duty wouldn’t either, but some would. How many would it take?
Really? Do you think human nature is any different in the USA than anywhere else in the world? History is full of examples of government police and military murdering millions of their own citizens. I can't think of a single instance where the police or military said "No, we're not going to round up Jews, middle class cambodians, etc." When David Dinkins outlawed semiautos in NYC there were no reports of any police refusing to arrest the "criminals" who kept their guns. In NO the police rounded up citizens' firearms. Not one report of any refusing to do so.
Don't count on any branch of the government at any level helping you out.