Originally Posted by Linguist

Not to be a thread pooper, but it's really up to the company to decide what's acceptable and what's not. If you wear a shirt with some kind of URL on it, be sure that people will be typing it in, and right there at the workplace. Is it appropriate to have that URL displayed at the workplace?

She had no idea it was adult related (shirt didn't warn her), and thus became offended... sounds completely reasonable to me. It's just like wearing the GFY shirt to work (no one forces you to look at it, but if you're amongst people, they will be looking at it).