One of the helpers took my dog out at 7 months and brought out his defense. Did this ruin my dog?

Hi Ed,

I have a quick question for you regarding defensive drive. When I purchased my GSD thru my breeder I planned on doing Schutzhund or Protection work thru them. We started obedience and have done really well at it. At about 7 months one of the protection helpers took us aside to "check his nerves" and basically brought out his defense. He did this for about an hour off and on by peaking around a corner and trying to get closer while Dakota barked louder or lunged at him. The next weekend he did this as well. After reading on here about starting them too early on defensive drive I am a little worried that we might have wrecked him. We have also done this at our house every now and then by having a friend trying to sneak into the house while Dakota was on leash and letting him bark and lunge. (Recommended by the trainer) We have since stopped all of this and just focused on his prey drive and play time. Im curious if we have ruined him in any way or if we are still ok. One thing I have noticed since then is that he will not have a prey drive when out of his element. Once he gets used to the surroundings then he will play all day but he needs to check it out first. He is now 10 months old. Thank you for your time and great website.