While at work on the 4th, one of my customers was wearing a shirt displaying the same sentiment. Numerous other similar stories abound, and I see people wearing clothes like this, or with some other vulgarity, all the time.
Forgive me for whining, by why? I've never been a firm believer in the mantra that clothes make the man, but what we wear says a lot about who we are, and first impressions are often formed by our appearance. I'm sure t-shirts with naughty phrases and raunchy pictures are funny to some people (I thought so too when I was younger), but most people don't seem to realize that that is the first part of your description that sticks in some one's head. If you want to be appreciated for your character, then let it show in how you display yourself.