training is a must. if you can get a professional go for it, there are no guarantees when dogs attack other dogs but ive seen it work.
i have had the same issue with my great dane and cats. my daughters syco cat attacked her as a puppy when she hadn't done anything. (this cat was huge not fat , 37 pounds beautiful, crazy, i trained it like a dog, but out of no where it would run up to even me grab with all fours and bite my leg then run) so we separated them. but every time the dog followed me into a room with the cat i would say no come on out she would turn to leave that cat jumped on her rear claw bite jump off. she hates cats. on the farm no big deal in town she hunts everywhere looking for them crazed.
it has taken a lot of work exposing her to neighborhoods with cat walking her but she is much better. but i still have to be on the look out be prepared. i would see a cat make her sit relax her telling her no cat while petting her get her attention back on me until the cat was gone and the crazed look left her face. difficult at first she pulled barked etc. but she can now walk see a cat i still tell her no come and she can hear me walk past without dragging or pulling most of the time. and when she start getting seems to start i real her in close stop until it passes. she will never be an off leash ignore the cats dog. but walking is manageable (she is trained to walk at my side on or off leash unless we are playing) if she sees a cat she doze not zone out into crazy where she cant focus on me. Treats help in the beginning and I carried a small squirt gun to initially get her attention so i could calm her down. not that she do sent like water loves it but it worked about 2 weeks i did not need it. keep him on a short leash right next to you, no pulling stop when he does, wait till he calms down then start A lot of praise when he is being good. stop pull him back put him right next to you sit then when your ready come. be consistent to what side you walk him on. usually the left but does not matter, when you see another dog command sit or down, if he dose not make him. then stay, pet him until he calms down and the crazy passe's. over and over he will get it until when he sees another dog he dose not pay attention to the dog he continues along with you. lots of praise. still i would not trust him off a leash around other dogs the liability is to great. it is never 100% if they have attacked before. you should enjoy your walks and when he is in familiar home and familiar other dogs you work on the same there a little at a time correcting him putting him in his place as to acceptable behavior. Cleo got sent to her room door open could not come out till she behaved it takes time ex poser energy. multiple times a day so they know how to behave all the time not just on walks or in the car.... you may have a problem with other dogs being off leash's running up to him the squirt gun works good here also tell the other dog no loud if they don't stop spray them. the owner is at fault and it is a gift to them that their dog isn't a fight, hit, pepper sprayed, just wet and its heir fault not obeying leash laws. try to
find a place and time you can have your dog off leash for play that is safe alone then start bringing one of his friends to work with him there.
hope this helps.
by petting telling her no