Saddam Hussein's gassing of Kurds in Halabja took place in 1988. Our governments at the time did not give much of a damn. The British Foreign Office issued a statement reading "We believe it better to maintain a dialogue with others if we want to influence their actions. Punitive measures such as unilateral sanctions would not be effective in changing Iraq's behaviour over chemical weapons, and would damage British interests to no avail." Saddam was 'our man' at the time, of course. Just as Assad was one of ours until not so long ago:
At left, John Kerry. At right, Bashar al-Assad. Their wives are in the middle.
If we take it for granted that Syria used chemical weapons when alleged in this conflict then those actions are not genocidal. Genocide and mass murder are not the same thing. Saddam's gassing of Kurds was arguably genocidal because it was aimed at a particular ethnic group and killed many more than are alleged to have been killed in supposed nerve gas attacks in Syria.
Many more peaceful protesters (around six-hundred) were killed in Egypt in 2013 by the military junta which seized power in that country after its first democratic election achieved the wrong result. We all looked the other way. As we did when around a thousand peaceful protesters were murdered by China in the Tiananmen Square massacre in 1989. The culprits of that atrocity are now granted state visits in the west.
In Syria, the information we received about chemical attacks was controlled by Islamist rebels who are allied with al Qaeda (the al Nusra Front). The OPCW was unable to investigate the incidents in accordance with its own protocols (except for the last one, where they found no trace of nerve agent). Where sarin-like substances were found, the samples had been passed to them with no chain of custody and no sarin-like substance was ever recovered by the OPCW itself. It was of no strategic value for Assad to use chemical weapons. He has been winning the fight, and the odd single-munition chemical weapon attack would not speed that up in any way.
Our actions in the middle east are fundamentally dishonest. We make a pretence that they are based on morality, when in truth they are taken in appeasement of Saudi Arabia, whose actions and aims are not moral, as we would recognize the term moral. Saudi policy becomes our policy. Assad is a monster, sure, but his opponents are lunatics, and it is only because of Saudi demands that we support the lunatics over Assad.