when and why would or should the military stand down and refuse to follow an order

None of these answers go to the question of how many soldiers would face off against American citizens should the order come down to "turn in" semi automatic weapons and the refusal that would follow. I had one SSG tell me that he would definitely go door to door to seize weapons. His opinion was that Germany had a better system than we do, and he was planning on retiring there.

Certainly you may be correct, however and correct me if I'm wrongt-I don't believe an order was ever given to fire on the protesting students in spite of the fact that had burned down the ROTC building and were responsible for other widespead damage. Remember one thing, it is always easy to be an armchair quarterback and criticize these soldiers actions after the fact-Do you honestly believe that the protesting students bear no culpability in what happened?

How about this situation: http://benswann.com/graham-military-force-congress/

https://www.rallypoint.com/answers/would-you-obey-an-order-to-restrict-congress-to-dc-until-they-increase-defense-spending

I think it's pretty clear that this would be an unlawful order, that should most certainly be disobeyed.