No, ofcourse not, because they are fighting. I absolutely have nothing against player's freedom when the rules are respected. But standing at the gate in peasant gear as attacker while time is running out and the gatecontrol is in the building above you can in no way help your team. Even if the defenders decide to abandon their castle for some reason, you shouldn't stop them as attacker. Running to the end of the map, where no enemy will ever look after you and you never have to fight isn't roleplay too. It is just unfair to your team.
He didn't got banned, because he is a nice guy that just wants to roleplay. His roleplaystyle is more like: "I am the landlord and can do what I want, I bump all that stupid peasants with my horse and teamattack everybody who is in my way. If they strike back I will just press "m". If I don't like to play I will stand somewhere around and gather XP in my peasant gear and watch my team doing the rest." You are wasting your energy to protect the wrong guy. He is just a troll, that ruins other players fun.