It’s more than annoying. There was a Company First Sergeant in my old unit (before my time, thankfully) and who ordered Soldiers to go to church, who ordered Soldiers to drive an hour south to his house to erect GP Medium tents (Army equipment) for church functions. I think that could certainly be termed “proselytizing” and it’s very inappropriate when done by people who hold actual power over others.
That’s the point of the (farfetched) threat of “court martial.” Such behavior can be detrimental to the good order and discipline of a unit. Since we can’t ban certain religions, and we can’t be sure the “good” religions’ representatives have a lick of good sense, we have to ban it outright.
That’s not about prostletyzing, that’s about abuse of resources and operating outside one’s delegated authority. There’s plenty of ways to deal with that without making it about religion in particular.