You can both empathize with the loss of innocent life, and understand that it was consequences of their collective actions. If someone where to stab someone, and that person stabbed them back, and the attacker dies, you can both mourn the loss of life, but also understand the attacker deserved what happened to them. Had we not accepted the warmongering, corporate, fascists, controlling our government, we would not have slaughtered 100's of thousands of people in foreign countries in the first place, thus avoiding the retaliation we received. That attack was defensive. Your previous comment implies that if a country is attacked by another, they should not attack them in return, because it would be underserved, which is just completely naive pacifism.

Yes, violence is bad.