It sounds like the trainer is trying to "flood" the dog..
Frankly, I believe, aggression can beget aggression
He may chill out for the trainer at the moment, but it may escalate his aggression in real life situations.
Personally, I would find another trainer..and pronto..
Tho both instances with YOU and the FRIEND, sound like he was resource guarding (he obviously did not want YOU taking the sock away and your friend the bone),,WHen a dog bites a person they live with, aggressively, that is one big no no.
Any of my dogs bit me like that, or even thought about it, I wouldn't need a trainer to take care of him, I'd do it myself, and they'd be sorry they bit the hand that feeds them
(I"m being sarcastic here, I don't expect you guys to do this yourselves)
I think you need to find (ask for referrals here on the forum for your area)..either a good behaviorist or behaviorist/trainer..I would NOT send this dog away, I wouldn't let this trainer touch a dog of mine ..
Your dog is only 8 months old, I don't mean to be harsh, but maybe you've been to easy on him? He sounds like he needs a good solid leader/training, or he may just be wired wrong
I would not trust him around anyone , you definitely need some help
Hope you can find a referral..