Saddam was an brutal dictator, make no mistake. But there are plenty of brutal dictators around the world that have come and gone, some still in place and some closer to home that the Western Allies would like to admit, that are 'allowed' to get away with murder, literally. The plan to remove Saddam Hussein wasn't done on humanitarian grounds, it was done as a geopolitical move by the west to influence Iraq and establish control in the area when Iran was the emerging big threat to the US. The result of that action has left Iraq and the surrounding area in complete turmoil.
They did the same in Lybia, when they removed Gaddafi and it's the same issue all over again with Syria. Bashir Assad was the new 'evil dictator', so Western forces moved in to remove him, although now look like they are backing him once again. In all scenario's they have simply caused a vacuum of power that is then fought over by squabbling internal factions, which the West doesn't know whether to support and arm to bring down the established Govt or to order air strikes on as being 'terrorist groups'
The whole thing is a bloody mess. And whilst the West urges the international community to fight these 'evil dictators' with their atrocious human rights records, they openly sell arms to Saudi Arabia who have an awful record of brutality and are currently pummelling Yemen, the poorest country in the Arabian peninsula, into oblivion.