If you consider Hillary Clinton's foreign policy, Iraq is part of a consistent pattern. Clinton vastly overestimates the utility of force.
In Iraq, the United States intervened. After ousting Saddam Hussein, and the Ba'ath party members that actually knew how to run the country, the country fell apart. The US spent nearly a decade fighting an insurgency there, and after the US left, the Iraqi state proved unable to govern large parts of the country. ISIS stepped into the ensuing power vacuum.
As secretary of state Hillary lobbied heavily for intervention in Libya. The US launched air strikes that may have helped oust Gaddafi, but did little to fill in the ensuing power vacuum. The result was renewed civil war, and a growing ISIS presence in Libya.
As Secretary of State, Hillary Clinton was a strong advocate of support for rebels against Assad. Many of the "moderate" rebels turned out to be Islamists, and as in Libya, unrest created a power vacuum that ISIS was able to step into. Worse, attempting to topple Assad ran afoul of the interests of Russia. While Russia is withdrawing from Syria at the moment, Clinton advocated a no-fly zone over Syria. This is a terribly risky policy, given that Russian planes were flying missions there. I don't know about you, but I don't think it is "nuanced" to shoot down the aircraft of a nuclear-armed state.
The ongoing drone campaigns in Northern Pakistan and elsewhere have been highly effective at alienating the Muslim world. In Pakistan, a vital partner on many issues, only 22% have a favorable view of the US. In Jordan it's 14% and Turkey, 29%. That's a problem because these are precisely the countries whose assistance we need in any sort of effort to contain ISIS.
Clinton has very much been seduced by the cult of the offensive that pervades the Pentagon. Military interests favor intervention because it means larger budgets and more control. Since the move towards a volunteer military, endless war is a politically easy choice as well.
There is a much better option (and it isn't Sanders - incidentally you're the one that made this conversation partisan). The United States should recognize that it can't overthrow strongmen without creating a power vacuum. It is also worth considering that terrorism is not a particularly big deal. Even if 9/11 happened every year, it'd kill far fewer Americans than corn syrup does.
But more than that we have to recognize that the United States is in serious relative decline. Endless war has certainly hastened that outcome, though certainly, all empires fall eventually. Historically, global leadership has been contested through violence. That's a scary prospect given the presence of nuclear weapons.
Rather than flexing our hard power, we desperately need to build strong global institutions that can allow us to maneuver the next century without a bloodbath. That means creating linkages with other countries through trade (I certainly applaud the Iran deal). And it means enhancing America's soft power. That's without even mentioning the environmental challenges we'll face (if we'd spent the $2 trillion we spent on Iraq on building nuclear power plants, and researching wind and solar - we could be an energy independent, low-emission country today).
You can support whomever you want to. But the choices we make reveal preferences. Claiming that your options are limited is a cop-out. Your individual vote will never determine the outcome of an election (and if it did, there'd be a recount). Nothing is stopping you from supporting and advocating a candidate (which may not be Sanders - maybe it's Jill Stein, maybe it's you running for president yourself) that shares your purported values more than Hillary Clinton. But the fact that you're waving away actions that led to the deaths of hundreds of thousands people, or calling dead Pakistani children nuances tells me more about your values than your "some of my best friends are black/gay/poor/brown" equivocations.