Peaceful muslims (if there is such a thing), do not have a problem with radical muslims killing non muslims.
True.. If the killers had boasted of being a Methodist, Presbyterian, Catholic or Baptist, on a killing mission...I think there would be an outcry from any one of those groups... immediately condemning the action in the strongest terms.
Same would go, if he claimed to be a Christian, on a revenge mission. We would all do our best to condemn such activity..