I don't think it's even likely to cause a problem wearing it in any casual situation. The people who are likely to be offended are probably those who don't get what it means anyway. Besides, how often do you really take notice of a small graphic on the front of a person's shirt?
May not be prime wear when you're hitting on a girl though, couse I guess that all depends.
![Wink](/tfp/images/smilies/wink.gif)