In any war there are victories and losses. There are attacks launched by both sides. To say that this attack was triggered by the war on terrorism is really one of those "no shit, sherlock" moments. The war is not over and both sides will continue to attack. Do you think the terrorist attacks will stop if we stop fighting back. They will only stop when their agenda is met or they are beat to a pulp so much that they can't function anymore. Remember, the WTC and Pentagon were attacked before we invaded Afghanistan and Iraq. There are some generally accepted ideas about what Bin Laden and Al Qaeda want, but I don't see many people suggesting that we should acquiesce.
An interesting question to ask is: How many terrorist attacks have been stopped or discouraged by the war on terrorism? You have to remember that this is not just a war fought by soldiers on a battlefield. There is a massive effort to locate and destroy the terrorists ability to function (money, communications, etc.) That being said, the retaliatory invasions in Afghanistan and Iraq have certainly made terrorists less likely to attack. If you get kicked in the balls every time you pinch the guy sitting next to you, you tend to stop pinching so often.