This seems to be the liberal cop-out every time these radical jihadists commit an act of barbarism against innocent civilians.
Not really. The cop out is, "Yeah, we were bad
then, but we're not now (at least not where we'll honestly admit to it). We didn't commit any acts of barbarism last Thursday between noon and 4:45 PM and they did, so there. It's them who are bad now." There have been times throughout history where Christians have been utterly barbaric, and times throughout history where they have been utterly not. There are times throughout history where Muslims have been utterly barbaric, and times throughout history where they have been utterly not. It doesn't matter whether it's recent or not, or whether it's Christians or Muslims, it's been done and it will be done again. It's religion being used to commit barbarism, no matter who does it or when. Neither Muslims nor Christians have an isolated, unusual account of barbarism that can be dismissed as an aberration. Both have regularly committed acts of barbarism on near-predictable schedules. Suicide bombers and cluster bombs aren't all that different (except our bombers are better financed and less suicidal).