Why is it that so many at Pride Marches tend to be a bit lewd in their costume and behavior?

I'm a gay man in his late twenties in Massachusetts and I have to confess that being at one tends to make me feel a bit uneasy. Not for fear of persecution, but, because I'm surrounded by what oft looks an orgy in pantomime. How is it that so many believe that showing such in public induces pride when all it may do is scare people to the other side of the argument against us? I really don't get it. I'm not suggesting that we should all be covered head to toe and that the atmosphere should be squeaky clean, but, I came upon a guy wearing just a black jockstrap in public at one in the city of Northampton recently and he was far from alone in wearing almost nothing.