It's a myth that feeding them raw will make them vicious/bite. Young ferrets (or even ferrets not handled a lot) are more likely to bite because they haven't learned otherwise. You can train them not to bite.
Feeding cooked meat is ok, feeding raw meat is PERFECTLY ACCEPTABLE, even encouraged, as raw bones can help clean teeth amongst other things. Never feed cooked bones (same with dog and cat) as cooked bones can splinter and cause internal problems.