Yeah, I think it's a better idea for the dog to be off leash at a dog park. For the reasons already described. Just like with most other things, though, it's better to politely explain to people why it's better than to be mean about it. The last time Finn went to a dog park, I had to leash him because he was just behaving badly and I didn't want him running around, causing problems. But, normally, he'd always be off leash. I don't think I'd take him if he had to stay leashed. But, if it works for you and it's not breaking the rules of the dog park, then go for it. From what I've seen at parks, the leashed dogs get picked on more than any others.