Local LEOsIt's not that simple, the would be lots of factors that would go into an equation before troops would be used in the manner you speak. First and foremost it would be local law enforcement, swat riot control etc, etc. It is not like you could wave a wand and have a whole Battalion of troops there. If said government building knew the revolutionists were coming, and said group was in the thousands or tens of thousands local, state, congress and POTUS would all have to bless off on utilizing the Insurrection Act. That would take time.
You say group I think of small element of people, which is nothing local law enforcement could not handle. I don't appreciate what you said about get of it you don't want to defend our country, I have read every single post on here and not one service member even eluded to not defending our country, it was quite the opposite actually.
Federal LEOs
National Guard
All before active military.