They had better, of course they do.
Marines don’t salute indoors unless under arms. Those Marines are not under arms. Marines don’t wear covers indoors unless they are on duty or under arms. Those Marines are on duty so they are wearing covers.
If a Marine is wearing a cover indoors, he salutes. He usually doesn't unless under arms, that's true. If he is covered he salutes. Marines are ALWAYS on duty if they are alive even in civvies. If you are covered for whatever reason you are saluting should the need arise. Part of the 11 General orders. Under arms also consists of the duty belt, hence the cover. This does present problems with other services' General. From experience.
thanks for the correction and clarification.
It’s been too long.
I was stationed at Stumps early 1970 and had to stop come to attention and salute a passing general’s car cause his stars were unfurled. He wasn’t even in the car. Too funny.