Well I don't see why you would have to put him down if he is attacking other dogs. If the problem is never remedied, simply don't bring him to an area with other dogs who are off leash and don't let him off leash.

If you are taking your dog for walks and on leash he likes to go after other dogs, try to teach him only you should be attempted to identify threats.

For example, well another dog is coming by, sit your dog down and praise him every second he is not aggressive as the dog walks by. This actually works.

If he goes after the passing by dog, correct the behavior firmly. A strong pull on the collar and a firm voice telling him no. Illusion collar, gentle leader or a regular collar will all work better than a harness. Chokers are downright dangerous and pinch collars have the possibility of making your dog more aggressive, although the possibility does not seem to be all that high.

So then move on to your controlled heel and watch where your dog only pays attention to you. You will need to start actually training daily if you ever want this, it won't exactly be easy, but one year old is not that old.

If you get to this point, you will never have a problem with your dog on leash again. Off leash is a bit more tricky however this is illegal in most areas and parks anyhow.

Also the socialization is great. Sounds to me this is not a dog who is aggressive but simply acts out from time to time with particular dogs. Well that is unless he is socialized with the same dogs every day and is only good with them. That is not doing much for the dog. If so start taking him to a dog park ASAP or trying to find other dogs in the area to make play dates.

If your dog ever dogs get in a fight, have a breaking stick with you, or learn how to break up a fight and control your dog. Pulling your dog by the leash or straight back is not enough. Get his legs off the ground.

He needs to be socialized with a variety of dogs. Now if you are already taking him to a dog park, and he meets a variety of dogs and only acts out on occasion, he could truly not want to be there, and possibly you are over socializing. He doesn't want to be there, he acts out, and the behavior becomes somewhat learned as acceptable especially if it was not strongly corrected.

Hope I helped and I see no reason why your dog would ever have to be put down. That is normally for dogs bad with humans. If you ever have to have another dog, say you move in with your girlfriend and she has one that will not get along with your pitbull, you will be able to find a home for a dog not good with other dogs very easily. If a dog is not goo with people you will probably not be able to find a home. No shelter would even try to find one. They would just put him down.

Let me know if this helped or not or if you have any more questions or something. Good luck.

Oh and don't be too nervous around your dog, he can sense it. Chest back, deep voices, dominate. Remember he ain't that big and scary anyhow