How do I delete an Apple ID from Apple TV 3rd generation?

I have a 3rd generation Apple TV (revised version from 2013). One of my friends signed in to my Apple TV to watch a movie, and he set it to remember the password. Now, whenever anyone else logs into my Apple TV, his email is always there, and I have to manually clear it before typing in any new email addresses. Signing out of any Apple ID does not work; my friend's email address is still there whenever I log in. Is there any way to permanently remove the email address without fully restoring my Apple TV?