we've got a very boisterous nearly 6 month old cocker who would approach every dog if I let him
I do think puppy owners bear a responsibility here too. If I see a dog on lead when we are walking off lead, I assume the owners don't want their dog to be approached by him and unless I hear/see a cue that says otherwise, I'll recall him and put him on lead to be sure he doesn't
if a dog is off lead, I would probably assume it was ok but I would still try and make eye contact with the owner beforehand and if they signalled it wasn't, I'd expect both of us to call our dogs back
the issue of course is when they are roaming fairly far away which does happen - if he's good with recall, can you just call him back? Frank has been attacked (while he was on lead) twice by the same labrador as his useless owner doesn't recall him (I imagine he can't but in that case, don't have him off lead) - I understand that some dogs will be nasty to puppies but I think the key thing is to make sure you can call him back before he has the chance to.