Jack

Question
We have rescued a beautiful Australian Sheppard when he was nine months old.  He was returned to a puppy mill where a highly aggressive male continuously was after him.  We took him and had him neutered.  He is now 14 months old. He is still very quiet and laid back. The problem is, anytime he is around a male dog of any breed, Jack loves to play and run with them.  They like to try to hump him.  
Any suggestions?

Answer
Jack appears to be an "omega" or at least a very low ranking individual by nature.  "Humping" is not sexual activity, it is rank related.  If Jack is willing to run and play with other dogs (instead of behaving fearfully as one might anticipate given his past experience!), let him.  He very much understands what another dog is communicating with the "humping" behavior and, providing there is no overt aggression (with injury), this shouldn't be a problem.