Why does United States view the Taliban as a terrorist organization?

I was going over some notes for my global affairs final and i was looking at the relations between US and Taliban. There was really no conflict until 9/11, and the conflict was that the Taliban refused to give location of Al Qaeda because the US failed to give them evidence for their allegations against Al Qaeda. Was that really enough for the US to designate them as a terrorist organization (especially after sharing some ideals e.g. war on drugs)? or am i missing something additional in my notes that may make it clearer? thanks