I take Dino to the dog park because he enjoys it. He is active so I give him exercise. Dino is very social, but occasionally there is a dog that he does not get along with so we leave. I don't see how its necessary for you to call people out on how they choose to exercise their dogs. If you watch for signs that a dog doesn't like your dog then you avoid dog fights, it's as simple as that. We are not repeatedly putting them in a bad situation, its a good way to socalize them whether you agree or not.
And since when are distemper and parvo the same thing? All of my dogs are vaccinated for distemper and rabies but somehow I doubt that the distemper vaccine is going to prevent parvo... You could be right but my vet never mentioned that.