Sorry but I'm with the others. You left your horse to professionals? They are not professional "gentle method" trainers, they are people who are paid to get the horse in the trailer.
I understand that maybe you were to shocked to intervene, but you should have stepped in and said "Ok guys, I appreciate your efforts but this isn't how I want my horse handled. May we go slower/try another day? I'll pay for your time of course"
You didn't say that, so they felt they could keep doing what they were doing, hey you were there, you were paying them, to them they had your approval.