Why keep troops there? The elected government of South Korea and its younger generation want to be juvenile? So be it, let them loose.
We pull out, the meat cleavers start falling on the peninsula. Sure, there'll be a refugee problem to deal with.
On the other hand, our companies will have lost their Korean competitors. That, and the reduced costs of not being in South Korea should count for something. Of course, China's satellite will have grown, but the lesson to the rest of Asia would be crystal clear. I suspect we may find ourselves with some stronger allies for the long run.
Please keep in mind that the current administration in South Korea is like our Dems, and does not represent many of its citizens. It did not win a big majority. Imagine if we had elected Kerry. That's what it is like in South Korea. Hopefully, they will get some realists elected in the next election.