What people are waiting for a Muslim 'mainstream' to define itself and tell the world 'terrorists don't speak for me'. The US, with its law and etiquette of free faith, would be a logical place for such Muslims to speak out. Why is this so difficult?
Moslems can't sincerly condem because their "faith" does not allow peaceful existence. The rule is "die, submit, or convert." There are no other choices.
They have to weasel and deny, it is the only way for them to buy time for themselves.