Isn't that what banning is supposed to do or am I missing something.
You're not a very good admin, nor person, if you're banning people purely to spite them.
Banning should be used to clean up servers and keep them running smoothly. Not to inflate an ego, or as revenge.
Sure, ban someone you don't like if that dislike will cause an issue, but if you're letting them on and letting them enjoy themselves, then banning them because they slightly annoy you once, or do something wrong on accident (which is most certainly what happened in this case), then it's just childish and spiteful.