This also happens in Austin, Tx near the "greenbelt" (trails and rock walls for climbing and swimming holes).
Behavior is taken seriously by the cops because it's associated with prostitution and drug use. Also something that some people don't realize, and that I didn't know until I was 17 or so, is that these type of crowds have been known to get aggressive and unruly. I first heard of male **** in Austin. I sat in on a ''date ****" seminar in HS and a crisis center person told us of the occurrence.
I think they only increased police patrols on the Greenbelt since it's such a popular spot.
Btw, I don't think the "powers that be" badger MTB'ers as much as they do skateboarders. So I don't think they are targeting MTB'ers.
Btw, the male prostitute, parks and "wooded areas" theme happens in all countries, Europe, South America... etc.