On AIBU, you are led to believe that all dogs on lead are so because they are anxious. My reality is that these are the very minority. Most dogs on leads in area where other dogs are not are so because of their recall, not because they are anxious of other dogs or reactive for other reasons.
I don't understand why so people here seem to experience such struggle in communicating. I find that it is perfectly natural to pick up on sign from the dogs and their owners. My dog seems to do this very well himself. He will make a very gentle move towards a dog on lead but remaining 2m or more away. I will make eye contact with the owner. They will either make a move for their dog to get closer to mine. Or I will ask if it's ok, and they inevitably yes, absolutely. Occasionally they will say that their dog is a bit reactive but still keen for my dog to come close, very submissively, and their dog reacts very gently. Only a handful of time as someone said that their dog couldn't be approached at all, usually in a very apologetic way, and I tell them that they are no reason to apologise, it's absolutely fine, I call mine, he comes to me.
I have my dog for 18 months now and it's really not an issue. Yes there have been instances when the dog on the lead started to bark at my dog when only 2m apart. That's fine, he just turns around. No big deal. I had time when dogs have run to mine a bit too eagerly (he is small size) but they have then been very gentle and it's been no issue.
I don't get all these supposed strict 'rules'. I guess you meant well, and it was silly of him to assume you were asking your dog to come because you thought his was aggressive.
In doubt, I just ask. A simple 'is your dog ok to be approached' with a smile. 99% of the dogs owner I pass on walks are lovely, friendly and laid back and so are their dogs, on lead or not.