I want to start this off by saying I'm kind of animal nutsy person and very very very very very pro spay/neuter.
So I totally judge people when I see their unfixed male at the park (because I cannot tell, unless they tell me, if thier female is unfixed). Personally I see no justification in not fixing a dog, and with the accidental litters I've seen in just my irresponsible stupid friends-well that makes me more judgy.
So when I see a dog with jangly boy parts -I judge the owner.
Anyways-will it cause problems-it can. I think it's often that the owner who is irresponsible enough to not neuter is irresponsible to not socialize and supervise and train [BIG disclaimer here=not ALL owners who don't speuter are irresponsible and many have good reasons-but for the most part....]and thus their dogs are problem dogs whether they are fixed or not.
That being said-and on top of that-I've been reading its not that the dog who is unneutered is a problem-it's that other dogs react to his testosterone and THAT causes problems.
At any rate-yes I'd prefer that all dogs who come to the park are fed safe diets (And aren't shedding salmonella all over) utd on vaccines and fixed. Are they? Nope. I just avoid the 'not great' dogs and we do fine.
So if you show up at my dog park with a dog who has jangly boy bits-I'll probably judge ya

but it's not like it's not been done and it will most likely be ok