It is sedition.
One (or more) military personnel actually take this as advice and act upon it, then it will go very poorly for said congresscritter.
Military personel are not required to obey illegal orders. They know this, and don’t need shit-stirring politicians to tell them. A General Staff, purged of Obama acolytes, should be able to figure out what constitutes an Illegal order. Any low-level troop that wants to act on their own political beliefs can do so, but they have to weigh the consequences. Insubordination is no small matter.
He’s more than a congress critter; he’s a former Navy O-6. I suspect he’d have been too cowardly to buck orders during his service time; some O-6’s spend a lot of time and energy eyeballing that first star, and politics becomes the rule.