I agree that being unneutered could be part of the problem. It might even explain why he has troubles at home and not when you lived elsewhere. Puberty in dogs, male dogs, is unlike humans. Koru may have reached the limits of his "puppy license." If this is the case you can expect unpleasant reactions to subside as he matures. What happens is, a male dog's testosterone spikes to 3 to 7 x what it will be in adulthood. This is like waving a red flag at some other dogs, both male and female. There's a good link here: http://www.dogstardaily.com/training/dog-communication
The problem probably won't go away completely as it is well known that neutered male dogs are sometimes aggressive towards intact males. In fact, recent research shows aggression in neutered dogs and bitches is more common than in intact. Here's a link to that article, which is based on CBARQ data: http://www.cdoca.org/downloads/files...20Behavior.pdf
Be sure to read this through. The summary says more aggression in neutered dogs but when you get to the breakdown you see there are some significant differences by breed and gender.
It's certainly not just a male dog problem. My friend's spayed GSD has been badly attacked by two spayed female dogs, on separate occasions. Both the attacking dogs are nasty to other female dogs, ok with males. Be careful with him, you have to look out for him.