whoa, how totally exaggerated by the people on the plane. if they are annoyed about a t-shirt so much than just don't look; it's not like someone forced them to look at it.
and even if they are in direct eyesight; the person who wears it still has the right of expression of opinion and if she thinks the people on the shirt are fucker than she has the right to express it.
and besides, I bet the shirt wasn't even meant to just annoy anyone, but just a bit of comedy.