You can't directly ask Microsoft to ban a specific person outright, but if you call Xbox Live Support and explain your situation, they might ask for his Gamertag and take action from there.
First off, try to make sure that you are trying to recover your profile correctly from the system menu. Incorrect passwords and e-mail can throw everything off if you're not careful. If you have your Xbox set to automatically log you in to Xbox Live, then you have a different problem.
He most likely changed the password more than anything since you can't delete a profile without calling Xbox Live Support first and proving that you are the cardholder of the account. By calling their support hotline (and dealing with the customer support from Satan's realm), you may be able to change the password from there.
Their support line can be reached from 1-800-4My-Xbox . Good luck and may the Live be with you.
