Lots of us frequent flyers have monthly subscriptions. So there may not have been a charge.
And some of us are tired of the "lets make up new rules because we are bored game" T
he FAs don't really get to "tighten the rules at thier discretion" on most airlines without a good reason and "I want to abuse my power" is generally not a good reason

And trying to claim it's an FAA regulation is an old FA trick. Just a few weeks ago I read a story where the FA claimed that the airline couldn't hold a plane for connecting passengers due to FAA regulations which require the plane to leave on time! OMG that was the funniest one yet. REALLY? In that case most US carriers should be bankrupt just from the fines for "leaving late" this FA claimed they would incur! LOL!
I wouldn't have bothered to look up the regs but if the FA had treated me the way he did the man across the aisle I would have sent Delta an email letting them now what happened. Of course he was kind of a jerk the entire flight.