I concur with LawDog. Lest we sink ourselves and become that which we despise, we should concentrate our efforts on those who perpetrated this act. Those who knowingly "harbor" them are, by olde English Common Law accessories before the fact or accessories after the fact. Either way, they're not innocent in my eyes and are legitimate targets.
Those who rejoice at the suffering of others are depraved of moral values. We didn't dance in the streets when Chernobyl melted down. We didn't jump for joy when India got flooded and thousands died. We didn't scream with delight when Japan got hit with the big earthquake. It's more their loss than ours.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!