That is too funny! He's like the man with a vasectomy who suddenly "feels free" and goes wild!! Ha!
Well, I think the humping is "less" after a neuter, but since females hump too and it is a "dominance thing" with dogs, I don't think it ever goes away completely. My westie is 5 years old and I had her spayed as a puppy but she still humps occasionally to show she is the alpha dog!