This is a toughie, especially if you have been to numerous behavorists & they dog has been doing this for 8 years.
Has he been doing this for 8 years?
If not how long?
How long have you had him for?
Is he neutered?
Didn't any of the behavorists help?
Were they reputable trainers?
Have you spoke to your vet?

It sounds like you need to seek help from yet another behavorist. And enroll him into a reputable obedience class.