How can we stand by when so many crimes against humanity are occurring?

We are missing the point.  Political terrorism is one thing; crimes against humanity is critically different!

Leaving political terrorism to be dealt with at the local level may be the right approach.  But today's crimes against humanity should meet a strong coordinated international response.

We have stood by while Boko Haram has committed unspeakable crimes.  Clearly, the government of Nigeria has been unable to defeat Boko Haram.  However, an international force should be able to encircle their hide-out area and deal with them relatively easily. 

Admittedly, there is a risk that hostages (the kidnapped girls) could be killed in the process.  I lack expertise in the methods that should be used to minimize such deaths.  But allowing Boko Haram to perpetuate its atrocities is not an acceptable position.  The risk of innocent deaths must be accepted to reduce long-term exposure.

Dealing with Boko Haram would be an example for others who would commit such atrocities.

We are also standing by despite an incredible wave of people fleeing their homelands for safety.  ISIS is not just a political movement.  ISIS's crimes against Shiites, Kurds, Yazidis and others constitute crimes against humanity.  How can we turn our eyes away from wholesale murder, enslavement and torture?  Rooting out ISIS is hugely more challenging than Boko Haram, but it also should be addressed by international forces.