I pointed out exactly the opposite: surely moral action is only possible when one has agency.

If an airline needs to force you to be a decent person, then you have no right to claim decency in the first place.

People who lean their seats back are assholes. Claiming “but this is permitted!” proves my point.

I can’t imagine what a nightmare world it would be if decency were only possible through the exercise of external authority.

And yet I'd prefer the person in front of me lean back and I lean back as well. The upright posture is painful for me. Is your preference more valid then mine? The fact that the chairs are configured that way suggests the cultural norm.