MSNBCMSNBC"What we're seeing taking place in Syria is heartbreaking," President Obama said during a debate with Mitt Romney last October, "and that's why we are going to do everything we can to make sure that we are helping the opposition." Senior Editor Jacob Sullum says that line was a warning—not only about escalating U.S. involvement in Syria's civil war but also about the lack of a credible argument for it based on anything resembling national defense. Judging from the explanation that Deputy National Security Adviser Ben Rhodes gave last week for Obama's decision to start arming the Syrian rebels, Sullum writes, the president painted himself into a corner with his own red line.