There are countless dictators, war lords and groups that go around killing hundreds or thousands of innocent people, doesn't mean the US goes in to help every time.
Assad may have been killing his people, in this instance those that opposed his government (in the same way the US would do a similar thing were a violent rebellion to spring up), but at the time the US (Hilary and Obama incl) supported the rebels, many of whom ended up fracturing in to ISIS, despite the fact that Assad still had majority public support. The decision to back the rebels was a catastrophic failure, since it aided in prolonging the civil war, and essentially ended up creating ISIS. Had the rebel groups not had political and military backing from numerous other sides, Assad may have quashed them, or at least sooner rather than later.
And it's funny you talk about the opposing strategy being an idealist leftist isolationist agenda, when the opposite in my mind is akin to murderous madness.
To go through a few of your other points.
What's cold hearted to me is directly or indirectly being responsible for killing or displacing hundreds of thousands of innocent people, which is exactly what US foreign policy on Iraq, Libya, Syria, Palestine etc has directly or indirectly enabled.
How about where the policies of taking out dictators got you? Or did you forget that this all started with the power vacuum that was left behind by ousting Saddam, based on an illegal war promoted through lies and false intelligence (a war which Hillary supported), that cost trillions of dollars of US tax payer money, and hundreds of thousands of innocent lives. The region was further destabilised by what happened in Libya, and of course Syria too. But it pretty much all stems back to the catastrophic decision to go to war in Iraq, and get rid of Saddam.
But we can go further to track the madness of hawkish failing foreign policies from the US.
Who do you think put Saddam in power in the first place? Who do you think armed him with WMD's and didn't care when he was using them to mutual interest? That's right, the US.
Who do you think trained the Afghani's in terrorism tactics in the hopes that they might be useful against the soviets? Again, the US.
Who do you think allied with Gaddafi, and even used his institutions as secret torture facilities when it benefited them? The US.
How about the US's constant support of Israel and countless obstructionist votes in the UN, that have essentially allowed Israel to colonise and slowly wipe Palestine off the map, as well as uphold a brutal occupation?
The constant support, both political and military, of Saudi Arabia, that has led to further dangerous ramifications?
How about who was responsible for overthrowing the secular government in Iran in place of the Shah, simply because Iran wanted to nationalise their oil? Again, the US.
And just to put things in to greater topical perspective, in Iraq, there were zero suicide attacks in the country's history until 2003. Since then, there have been over 1,900. In Pakistan, there was one suicide attack in the 14 years before 9/11. In the fourteen years since, there have been over 490. United States foreign policy and military intervention continues to be one of the, if not the biggest indirect catalysts for terrorism out there.
There are so many more examples of how reckless, evil, damaging, and absolutely disgraceful US foreign policy has been over the years, especially in the Middle East (which is not to say certain other nations haven't also shared responsibility or had similarly reprehensible foreign policy), that I have to wonder how anyone could possibly actually be in favour of the status quo, or such repeated failing strategies.
