"You don't know 'who' will use 'Hitler' until you listen ;))"
You got me!
But once someone Hitlers, there's no point in listening any further. It's just good versus evil ever afterwards. And US self-interest is not simply "good".
I agree that Assad is a nasty piece of work. But we'd have been better off with a gradual,managed shift towards democracy than what we have got. Both (or all) sides seem pretty rotten.
As regards O's foreign policy. He was a fool to snub Russia over Snowden. Now he needs Russian help about something important and he's not going to get it. At least not easily.
Syria is a key strategic Russian client. It isn't about human rights or democracy for Putin. He needs a Mediterranean base for his navy and he has it there.