Papillion, unfortunately you didn't get the best advice there from the breeder. Its actually better to desex them behaviourally before they start to adult behaviours. This is because sometimes the behaviours are difficult to reverse once they have started. Some do work.... so the first thing to do is get him desexed and hope that will stop the behaviour. If that doesn't work there are more in depth training things that you have to do. Its best to desex first and see if that works.

ETA: Teegz I don't mean to disrespect the way you have trained your dog, but I think as someone who has worked in the industry for over 10 years that its a dangerous technique to suggest anyone to use. I have gone to multiple seminars regarding the chain throwing technique, some were for guard dog training, and some were passionately anti chain throwing. I do know a lot about that particular technique.