This is called "ceding the moral high ground"... If I were Muslim I would be condemning them for blasphemy for claiming that this was what God wanted by screaming that "God is Greater" phrase while they commit such barbaric atrocities. Killing the innocent is forbidden in their religion and none are more innocent than the children.
Any sympathy I may have felt for their fate is gone. It was fleeting to begin with, but now they have dehumanized themselves.
Agreed their actions should be condemned. If the Muslim nations continue to support this, it will not be good for them.