And another thing about Fahrenheit 9/11: Moore makes much of a visit by a Taliban envoy to the state department in 2001. "Why on earth would the Bush administration allow a Taliban leader to visit the United States knowing that the Taliban were harboring the man who bombed the USS Cole and our African embassies?" Moore asks.

Because the Taliban envoy brought a letter to Bush containing an offer from the Taliban in an effort to resolve the question of what is to be done with Bin Laden.

Thats why.

(source)