Cameron is planning to sack ministers in revenge for a defeat he engineered himself. He made promises he couldn't back up, he misread the mood of the country and the House and he went into the debate without having properly prepared his case. He's the one who should be out of a job.
How many civilians have the Western Allies- meaning America mainly- killed in Iraq and Afghanistan? Are those killings less heinous for being brought about, not by chemical weapons, but by shells, bombs and bullets?
In order to punish Assad for killing Syrians we're going to kill some Syrians. Now where's the sense in that?