What was he doing in a park "day after day" trolling for women?
Anyway, from what I've read of it, it sounds like entrapment. Particularly with the touching. But there's a context from this case that's missing in order to drum up controversy.
I'm not saying this guy is not a pervert, he very well could be, but when a hot topless woman, who is touching him, asks him to take it out and he gets busted for doing what she asked...
There just has to be something the article isn't saying because that sounds like the very definition of entrapment. If she did not ask him to take it out, then I would agree with the conviction, but (according to the article) it was her idea for him to break the law.
entrapment: "the luring by a law-enforcement agent of a person into committing a crime." - dictionary.com
*edit* I just thought I'd add that since they have no evidence of him being a repeat offender, they can not use the fact that some people use that park to masturbate and have sex to convict him. It could just be he likes to pick up women at that park and was a perfect law-biding citizen before he was asked to do something illegal. It's very possible thats not the case, but there no evidence that its not (at from what that article says).