The guy does have a point though.
There are still rules. If it only happens at night and used condoms aren't left around then, it doesn't seem to be harming anyone. It's not something I'd encourage, but I wouldn't get myself wound up about it.
Dogs off the lead, on the other hand, are dangerous. They can scare children, they can bite and they're more likely to leave droppings around the park. Droppings that can harm the health of children and even lead to blindness.
That does need clamping down on.