I'm no expert, but it sounds to me liked learned behaviour - and what has been learned can be unlearned!
I recently adopted a lovely 8yr old male from Jan. He's a typical fabulous goldie, but I soon discovered that he was incapable of walking past another dog whilst on the lead, without lunging at them and barking furiously. He would never bite or fight, but it was quite worrying; other owners certainly didn't like it and it made me anxious to avoid other dogs en route to where I could let him free-run. Even then. he would sometimes run up to other dogs when off the lead and bark at them and skip round them quite noisily for a few moments before losing interest.
So I contacted a local dog trainer with a good reputation and to cut a long story short, we had 5 lessons with him and bingo, perfect behaviour! It took a lot of effort between sessions to maintain what I learned, but it has paid off. I can take him anywhere now on or off the lead and not worry. In fact everyone loves him on our walks -he's quite a character and sooo handsome!
I really can't say all the strategies I learned in this post. I just wanted to say that I think if you find the right trainer, please be assured that you can learn how to work with your dog to change his behaviour. I know how unsettling it is to feel anxious about your dog's behaviour when you're out with him. I live in Yorkshire and can recommend the trainer I used, but I don't know which part of the country you live in.
Good luck!
