Aggresive towards other dogs

Question
Please help.
I just bought a year and a half old bulldog and things were going well till he sees other animals.  He tries to pick a fight every time and the other day, he bit the nose of another dog.  I do not want to get rid of him, but this could be the beginning of a huge problem.  When I walk him, we pass tons of dogs and it seems like the training I have been doing goes straight out the window.  I really do not want to get rid of him, but I might have to.

Answer
If this dog isn't neutered, he needs to be right away.

You also need to find a trainer with experience in behavior modification. This is a workable issue.

My suggestion would be, when you have him out for a walk and another dog approaches, give him the "sit" command and make him stay there until the other dog passes. Take him off to the the side so he doesn't see the dog as an approaching "threat" but rather as just a passerby.  When he allows a dog to pass without showing any aggression, praise him greatly. When he does show aggression, demand that he sit and stay.

If it's possible perhaps to sit with him and just let other dogs pass, on a bench perhaps, and just let him see that the other dogs are ignoring him, that might help too. It seems that he's had to defend himself at some point in time and he hasn't forgotten it.

Again, if you can find a trainer, he/she may be able to offer better suggestions than I.