We all did.
By participating in religious wars since the Crusades, agitating sectarian violence for millennia, feeding into secular schisms, and it hasn't changed much since the 11th Century and before. Some parts of the world like the US, have progressed, but other areas of the world haven't changed much since the 7th Century when Muhammad was alive.
Secular violence has killed more humans than any other disease in the history of the world. Even the Black Plague was a mild head cold compared to killing that takes place in the name of God.
Why did I say we all did? Because some feel that what happens in some other part of the world is not our problem. On the other hand, some think that it's our destiny to take our religion (democracy and capitalism in some cases, or a different religion of God in others) to everyone around the world. We have a responsibility to protect the vulnerable, not just here in our own country, but elsewhere as well. We did so in the Balkans, and those we protected were Muslims, so their religion wasn't a factor to us, although that's why they were being exterminated. We did so in Europe in WWII, where religion was also the reason for the genocide, but religion wasn't the reason we got involved. But we tend to look the other way lately when it's politically incorrect however, especially if there's oil involved, or it could effect our oil supply.
This particular example of genocide is a little different than what we've seen on the past from a geopolitical standpoint, but the fact that it could inflame the Middle East and effect our oil supply makes it a hot potato. The fact that Russia and China have opposed any intervention has also scared, yes scared our politicians in power. But the horror is no less real, and our responsibility to protect the vulnerable is no less relieved.
Sitting back and watching is not what we as a capable group in the human race should do. Making blustery statements about red-lines and then doing nothing isn't either. Using the excuse of having to get approval from the UN, which cannot agree on much of anything, and Russia or China could veto any resolution, isn't either. Getting a coalition together of like minded nations is a good idea, but it should not be a 'go/no go' line we have to cross before we take action to protect these babies.
A strategy of actions that can progressively escalate when and if required, such as what President Obama is reportedly looking into now, is exactly what we should be doing. Do I like it? No. Does that mean I will not support the President if he makes the decision and gives the order? Of course not. Most things that are worth doing are hard, and uncomfortable. And the choice to use force to protect the vulnerable is no different.
We should still stand for something in this world. Not expansion of our power and control, but standing for human rights and protection of the vulnerable. We should protect our economic interest around the world as well, but protecting the least among us from genocide shouldn't even be considered a debatable political choice. There is no choice, because the alternative to action is to be complicit in the murder of these children and those that follow, and that... is an unthinkable result, and is a thought I would not want to live with if I were the President.