We have two RR bitches. Both are well trained and loving. We are house-sitting a RR male, 20 months. He is extremely loving towards us and adores me (male). However, he has a frightening trait. When off lead and unexpectedly, he will suddenly charge towards certain (not all) male humans, barking loudly and jumping up. It must be frightening being on the receiving end. The dog stands six feet tall when on his hind legs. In our country, the dog will be ordered put down for this sort of behaviour. He is not trusted by us off lead, whereas the two bitches walk calmly by our side. A breeder (not from this dog) has indicated that this is a RR genetic trait that breeders deliberately "breed out" of their packs. Does anyone had similar experience with this breed? Other than good solid all-round training, has anyone any suggestions on how to specifically target this behaviour?