Yeah, biting shouldn't ever be tolerated. He needs to know who's boss, & that it's not respectful. I'd smack him on the neck or shoulder. I knew a horse who used to bite when I was about 11, & she finally stopped after I gave her a few good smacks on the shoulder. Not hard, of course. But it taught her who's boss. I also don't like to 'hit', but some discipline's not bad...especially if they're biting.
& biting them back? Lol, I've never heard of that...but it may work as well!