Agreed, that deterrence is a good thing.
If you received launch orders, then the picture changes. What if those orders are offensive, rather than defensive? Would you have refused to initiate a launch, and be court martialed? What difference would that have made, if you did?
There are provisions in the UCMJ to disobey an illegal order. However, whether a military action is offensive or defensive (the most common difference between a just and unjust action) does not fall into this category of exclusion. Additionally, real conditions, orders are followed, unless the commander is clearly incompetent, or poses a danger to his own unit. For example, I have seen an order given for a “danger close” air strike, that is an air strike which violated safety rules and could have resulted in friendly casualties. In that case, the gunny refused the order, and the colonel giving the order was too incompetent to call in the strike himself.
So, that was an example of refusing an order. But, it was a very unusual one. Military personnel follow orders. When you sign up, then you agree to do that.