I agree. This is publicly giving Trump the middle finger. The title itself shows how everyone will take it: “Navy secretary DEFIES Trump”.
How do you have a military where anyone can openly and publicly defy their superiors? Complain in private? Fine. But once your commander decides, and the decision is legal, all discussion ends! Salute and obey. We fought to PROTECT democracy. We didn’t practice it!
You are correct about salute and obey. But you have to have an order first. The President extrapolating on twitter is not an order to anyone. It is his thoughts on the subject. If he is serious, I believe he is, call the SECNAV, either to the oval office or on the phone, and give him a direct order to cease and desist with the review board. If he does not follow the order, fire him then.