Yeah that dude is not only wrong, but a f***ing stupid human being as well. Politely ask if the person wouldn't mind reclining less. If that doesn't work, then suck it up for the four hours you're on a plane, you'll survive. Punching the seat repeatedly is a kid's move.
The only reason there's any debate is because internet argument logic boils down to right vs. wrong with no room for nuance or courtesy. You could technically be right in a lot of scenarios that would still leave you looking like an asshole (This guy, maybe, for example).
There's a saying that a smart man knows a tomato is a fruit, but a wise man knows not to put a tomato in a fruit salad. A lot of internet debates boil down to like half the people arguing that the tomato should go in the fruit salad. Just stupid.