I'm pretty much in agreement with Jim, Bilbo, Ono & Amat. It's obvious why they were doing it. Not to mention wearing a t-shirt with a flag on it is lame unless it's affiliated with sports. But really come on. If I turned up to the US on Independence Day with a t-shirt with Osama's face on it* (and only wore it on that day), what would you think my intentions were?

* For all the thickos whose reading comprehension is terrible, I am NOT saying I'd ever wear an Osama t-shirt, it's an analogy.