Calling an attack by Islamists "senseless violence" also absolves you of having to identify and understand an enemy. Hey, man, these guys are just crazy! Who knows what they're going to do next or why? "Senseless" means you don't have to develop a strategy outside of taking all sharp objects away from everyone.
In short, this is the attitude of people who think that their way of thinking is the only way. They're on the "right side of history." Anyone who disagrees with them is clearly crazy. That list of crazy people includes you if you don't buy into their view of the world.