The horrors that Yazidas suffered was solely because Obama left Iraq too early. Mosul was overrun by ISIS and Christians were slaughtered for the same reason. ISIS became a threat to national security for the same reason and we had to go back destroy them.
Something similar would happen if Afghanistan if we pulled out altogether.
re: Afghanistan. It never made sense. We were at fault for letting Saudis illegally stay in the US. It would've made more sense to be more careful about who was in the US than to get involved in Afghanistan.
Now, why not let the Taliban have it? We're supporting a corrupt gov and paying off lots of people to be our friends. I care less about them than innocent victims of our warmongering ways.