That something utterly appalling happened outside the Syrian city of Houla on Friday is beyond doubt. As the sickening pictures of murdered children showed – pictures rightly reprinted by several British newspapers, including our sister paper The Independent on Sunday – many victims were children, at least some of whom had had their throats cut. Even as the Syrian authorities denied responsibility, blaming Islamists and terrorists, they conceded that at least 90 people had been killed. Of these more than 30 were children, slaughtered, as the pictures attest, in cold blood. Opposition activists accused pro-regime gunmen of the massacre.