They could be interpreted as bombs... among other, easily as offensive, things. The problem here, I think, is that no matter what the turban had ended up being they would have been offended. The point now is translating the offense into political capital. Engineering the offense seems to have been pretty easy.
I mean, though, when people say to me "Aren't people always going to be offended by something or other?" I'm like "Does the Pope crap in the woods?" Or is it, "Do bears wear funny hats?" Or something like that...