Banning should be a function available only for admins whom might be more responsible in judging some players actions or because it's his server and he feels like banning someone will set him free.
Banning should be the ultimate option and unavailable for users, an admin present on the server should first try to educate the crazy guy and explain the server rules or whatever he done wrong and if all his efforts fail then ban.
As for the users kick action should keep an unwanted player away from server let's say 5 min first time then 10 min and so on like the "too many clicks" system when you try to join a full server and you go crazy connecting.
I've seen "bands" of guys on drugs having stupid fun bannig racers on a server and then move on to another until they get bored or not .... you can't race on that server so it's better to move on and search for a proper server.
I'd suggest when something like that happens to save the mpr and email it to ppl in charge and maybe they can suspend their licence for awhile to cool them down.