You're scaring me now, I'm worried that Oscar is becoming fear aggressive when he has previously shown no signs of aggression whatsoever, he just wants to play all the time.

He doesn't do it to all men, he's barked at a couple jogging, the one today looked as if he had a slight mental disability and he was terrified of dogs (I was with someone else with dogs and they seemed to think Oscar was trying to play but the guy was re-coiling), another guy he barked at was shouting across the road to us as we had broken down and the other time with my friend walking in the woods with his wife and grandchild, the little girl was swinging a stick about.

I'm worried that he is feeling my apprehension when people approach because he is so exuberant with his greeting. If they have a dog with them he seems happy to interact with men.