I'm never worried about someone learning commands and turning my dog against me. They can shout all the commands they want any dog worth a crap knows the difference.
That said, take any handler and roll him on the ground with a bad guy, a lot of dogs don't know who to bite and often bite the wrong guy. That's why it must be trained. A dog that has been thru that training is fine, but take one that hasn't been, pair him with a new handler and put him on the ground in a scuffle? he's as likely to get bite as the bad guy.