Dog aggressive towards pit bulls

I wouldn't read too much into it.  Since your dog is still a baby, it is likely he will still change a lot.  Many GSDs won't tolerate other non-pack dogs once they are mature, though some (like mine) that go through more reactive periods as youngsters mellow out and are stable around strange dogs, but don't have any desire to interact with them.  I don't know how Huskies are with other dogs but I know how GSDs are and as a breed, they can be dog-aggressive and pushy dogs with a high pack drive which means loyalty to their humans and dogs but aloof towards neutral strangers and aggressive towards threatening or pushy strangers.  There's nothing wrong with having a dog that just doesn't care to be best buds with other dogs, whether they are pit bulls or not.  There may be something about their play style that your dog in particular does not like.  Intolerance is not necessarily a display of dominance.  I know several pits and bully breed dogs that are very sweet, social dogs but have a very in-your-face style of interacting with people and dogs (one muzzle punched me really bad on Tuesday, didn't mean anything by it, luckily I turned quick and didn't get hit as hard as I could have or I would have a black shiner right now!).  My GSDs won't tolerate that style of interaction and it has nothing to do with putting on a display of dominance, they just don't care for it and will tell the dog (in their own way) to knock it off.