It sounds like this guy had some very rude dogs, poorly trained around other dogs besides each other. Typical of dogs who have been raised together since puppies. Its kind of pack mentality but neither pack member is aggressive enough to start a fight, they're just putting on the show of dominance together. I have a neighbor who has two pugs who do the same thing to Autumn except he's working with them. If they were not going too far from their owner and you had a big enough park you probably could have walked far enough away from them that they'd go on to some other dog to harass. Pack dogs are the worst, even if they aren't aggressively attacking, I avoid people with a tight-knit pack at the park.