1) It is inappropriate and probably against the code of conduct.
2) Good luck getting these guys to support an anti Trump coup.
Code of conduct? LOL! Is that the same UCMJ that demands I accept men dressed like women, that I accept two men kissing or worse in the shower next to me, that I not accept a Chaplain uttering Jesus outside his chapel, that I accept women being given a Ranger tab to satisfy the homosexual Secretary of the Army? To hell with the code of “conduct.” President Trump needs to send out a tweet today, Thank you to the Navy for flying my flag. That would be the end of the conversation.
It’s been a long time since I had anything to do with the UCMJ. I know there is a connection to political campaigning, but if (as I posited) this was after the election then it really wasn’t campaigning.
As for being in appropriate, I don’t think so. Indeed, what if ever, happened to those GIs in the Mideast with the “Halp Us Jon Kerrey” signs?
IMO, a judge advocate would have to be nuts to prosecute anything about this under UCMJ.