I suspect small dog owners who behave like that are "over-compensating" for their personal "short" comings. I just don't know about a dog that my cat could eat. Course, my 10 lb cat forced a 100 lb Wolfhound to back down. That cat takes crap from nobody.
The dog park I used to go to had the weight split as well. Never had issues while I was there. But the big dog area was larger than the small dog area...probably because the dogs are large and need the space to run. Hence the whole point of a dog park. Most people in the large dog area were great and cleaned up the poo or provided water for all dogs.
As far as large dogs, I've met some great ones and met some that we kinda a-holes. I think 90% of it is how they are raised. Met a rottweiler once that really was just a big lug that wanted to be loved. He liked to eat bricks. Like literal bricks. I'd like to get a large dog like a Newfie or Dane, or a Cane, or Tibetan Mastiff. But getting that past the boss... Plus I don't have the time to properly train a puppy. Unfortunately.