Well, personally, I do believe most of them will. Too afraid to buck the brass to defend the Constitution - after all, lawful or not, Constitutional or not, they "ARE", orders.
Years ago the Marines were given a survey - back in the 90s - and said if they were ordered to kill US citizens, they would, and so would (two different time frames) a young man working in a dive shop in PCB who was currently with the Navy, and one working in a local auto parts store in PC, then with the AF.
Go and ask some questions. Or maybe just one. The one in the heading.