Oh for cryinoutloud . . . everyone is so sensitive.
Yes, the guy that "helped" OP definitely over-reached. With him, I'd make a joke like some that have been suggested. On the other hand, if OP is diving with these big brothers on a regular basis, maybe he's not an ass but a kind hearted soul who misunderstood the need for "help" at that moment.
I've reached over and flipped this or that for another diver without them asking. Sure usually say "excuse me, but your weight belt is upside down" or whatever. True, would not be checking anything more than buckles and such on another diver's bcd without them asking, and then would only touch the buckle or whatever while saying such as "excuse me, may I get this twisted strap for you . . . ?"
But there must be many many of my fellow divers that have wondered why I was fooling around behind their butt on the seat, when all I'm doing is untwisting something.
By the way, I'm female and prefer not to buddy with a stranger . . .but we are still all "buddies" on the boat. Let's watch out for each other.
Men? Heck I only understand one thing about them.