You say that like you think there's a right side ...
Nope, but there is a "least worst" side.
I will point out again, that prior to Hillary mucking around in the ME, was that Syria was a secular, pluralistic society. Muslims, Druze, Christian, Alawites, and other (but not Jews) were free to practice their religion. The country has been mostly peaceful (for given values of peace in the ME), and at last report fought on our side in DS/DS helping free Kuwait.
Enemy of Israel - You betcha.
Funder of Terrorist groups - Bingo.
Poision Gas and potentially other WMD's - Probably got them from Iraq. And he's used them. Also got rid of all of them. (I'd bet money that the last use was either faked or done by "the rebels"
My point is that "the rebels" are radical Islamist Nazi-esc f*expletive deleted*tards. If our option is to only back "The Good Guys", then we need to nuke the entire ME, and repopulate it. But since that would make us the Ultimate Bad Guys, we need need someone to ride herd over there. The Assads managed to keep those f*expletive deleted*tards in check for 40+ years, while allowing everyone else to do their own thing.
If we team up with Russia (another country run by someone with lots of blood on his hands), and Assad then we can beat ISIS (and other sub-groups of Islamist f*expletive deleted*tards), then we can put the screws (or before) to get Assad to stop funding Hamas, Hezbollah, and other terrorist groups