The parks weren't just being "used", people were littering, staying after hours, trampling on flowerbeds and stuff. Or did you miss that part of the article?

So many normally sedentary people were getting up and going out and doing shit and getting exercise .. and people still went out of their way to be dicks about it... I don't get it.

Say what you want about the city's misguided attempts at enforcement. But by no means was it in response to "normally sedentary people getting exercise."