First off no slaughter would be necessary just ‘friendly’ intimidation. Simply suspend Habeus Corpus and Posse Comitatus due to eminent threat (the GOP in Congress would mostly go along) and arrest a few thousand trouble makers. Every President of both parties is familiar with the Abe Lincoln playbook and this operation would be a very big version of the US government's takeover of Maryland in ‘61. Americans are not going to risk their lives and property in a situation where they will be confused by misdirection and mis information and manipulated optics on a grand scale. Active measures will be employed. Little shooting but much propaganda some of it armed propaganda.
Most of the Army mid level personnel I met where either middle class careerists focused on paying the mortgage, getting their pension and figuring out post retirement employment or uniformed bureaucrats. The warrior ethos has about expired in much of the Army other than the ever smaller slice that are true combat arms types.
Okay, I get it. We’re playing comicbook scenarios.
Let’s do it: How will the DC politicians deal with the 2ndMarDiv coming up I-95? Remember, now, that the 2nd Marine Airwing will be dropping napalm to soften up the heroic DC politicians.