The military, among both officers and enlisted, is actually pretty split politically, and a good number can and will refuse to obey an order they perceive to be unconstitutional, or outright commit mutiny. For all that the military warns about insider threats, it is also woefully unprepared to deal with them as well. Military servicemembers are also significantly stricter with the use of deadly force than police from my experience, although that may simply be due to my having served in the SSBN force.