This is based upon the comments to the Random Pic blog below.
Yes, a man was arrested last week in Decatur for "rubbing himself" on a slide in a park. The bad news is that the most he can be charged with is a Class C Misdemeanor (Disorderly Conduct) punishable only by a fine up to $500.
Not to get graphic, but the facts are that he rubbed himself over the clothes. Nothing was exposed. With that, you get yourself a Class C - the equivalent of a traffic ticket.
Don't yell at the cops. Don't yell at the prosecutor. Don't yell at the judge. They are bound by the law and that's what the law is.