Assad is a particularly horrible bogeyman for the Left. He has survived by protecting the minorities, the Christians in particular, in Syria as he is a minority Alawite and his power base is the minorities. And he is an Arab in an Arab country thus he is vicious and quick to wipe out misbehaving groups. Once upon a time I was horrified that his dad leveled the city of Homs because the population there was mounting an insurgency. I know better now, that is what Arabs do and a ruler has to be ruthless to survive and to govern/rule an Arab population. There are also Kurds and the Azeris, Druses, Alawites and more.
Ruthless people should be governed by ruthless leaders. Not saying all muslims are ruthless, but some muslims are ruthless. They’re not a good fit with western society. It doesn’t work. Oil and water.