You're saying there is a moral equivalence between Britain, which had been relentlessly attacked with bombing raids on civilian London, bombing Dresden and Al Queada, a terrorist group that had previously attacked numerous civilian targets and suffered almost no retaliation to date, flying planes into the WTC towers and the Pentagon, again killing mostly civilians?
If you start terror bombing civilians, then you shouldn't be surprised if your opponent retaliates. Some may be surprised to learn that the British, not the Germans, started terror bombing civilians deliberately. The RAF Air Secretary admitted it in his book.
From: Advance to Barbarism: The Development of Total Warfare from Sarajevo to Hiroshima (Paperback)
by Frederick J. Veale (Author) on Amazon.com
". . . The accusation leveled against the Germans that they deliberately caused harm to civilians is refuted by the fact that the British started this breach of international law. Veale cites J.M. Spaight's book BOMBING VINDICATED to prove that the British started the deliberate bombing of German civilians on May 11, 1940 which Spaight called the "Splendid Decision." While the battle for France was being waged hundreds of miles from German civilians, the British, who should have focused their bombing to military targets such as bridge networks in France, instead bombed innocent civilians who had nothing to do with the Battle of France. In fact, Veale makes a good point that had the British concentrated their bombing on these bridge networks, destruction of these networks would have stopped Hitler's mechanized forces due to the lack of getting gasoline supplies. The German offensive would have stalled and would have been defeated."