Bashar al-Assad could easily be (and mostly still is) a bastard like Gaddafi and Saddam were, but still he is a 'civilized' and 'secular' leader. Whatever iron-fisted brutes Saddam and Gaddafi were, they still were better than total fustercluck boiling now in (former) Iraq and (former) Libya.
As for me, secular tyrants with hospitals, schools and working infrastructure and social services are indisputable better than XVII-century-like tribal and narrow-minded warlords (and their respectable daredevil Sharia governments).
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Russia would do nothing, just sit down and exclaim against all of this in the UN along with China. Iran would probably be involved in the proxy security raids.
Putin just doesn't have the mentality to strike sparkles with EU/USA.
Syria would be just consumed by civil war madness in all its ISIS gory and glory.