According to QANTAS

"Whether made verbally or on a T-shirt, comments with the potential to offend other customers or threaten the security of a Qantas group aircraft will not be tolerated."
-Qantas spokesman

Since the T-shirt describes Bush as the World's #1 Terrorist, it's true that it has the potential to offend other customers, but was this really the clause that blocked boarding, or was it the potential to threaten the security of a Qantas group aircraft? Exactly what would happen if the World's #1 Terrorist knew that Qantas was aiding and abetting a promulgator of anti-Bush sentiments? Perhaps the people at Qantas realize how dangerous that would be.

Comments

If I ever fly Qantas, I will make sure to wear a t-shirt that says "I HATE PUPPIES!!!" Or maybe "I HOPE THEY SERVE PEANUTS ON THIS FLIGHT, ALLERGIC SUCKAS". But then again, what DOESN'T have the potential to offend other customers?

I'll go for a T-shirt with
"Hand over all your chocolate and nobody gets hurt"

It'll be no real security threat until some pitiful trembling soul hands over a carob bar...