I suppose I meant the really truly aggressive dogs who react at the mere sight of other dogs I've never seen anyone bring such a dog into a gated park, but there surely are some folks who probably would do that. We should also keep in mind that a laaaarge number of dog-reactive/leash-reactive dogs ARE frequent dog park goers and ARE very dog friendly. Because it's so much more complex than dog friendly vs. dog aggro, I just choose to avoid parks altogether. It's fun stuff watching interactions, though. You really get to see the intricacies of dog communication