Hmmmm.... seems to me that Mohammed set about to convert the known world to the Religion of Piece at the point of a sword and that his successors relentlessy attempted to conquer Europe for a period of seven hundred years.
Had he forgotten?
Apparently so. Depending on the type of soap used one could forget most anything.
My way of looking at the scenario (without religion being a factor, just common sense) is when somebody has the mindset to kill innocent people the reasons they have to do so are irrelavent.
To accidentally without provocation kill innocent people in the process to annihalate that threat to large numbers of innocent people (I.E. after the trade towers debacle and the threats of violence being conveyed by some), defending one's self from further bloodshed I consider that reasonable in the eyes of God.