These are the isolationist Republicans (whom McCain famously dismissed as “wacko birds”) — folks like Sens. Rand Paul and Ted Cruz — who oppose Obama’s plan because it is too vigorous. They don’t support even a limited strike on Syria because they don’t want America involved in the conflict — period.
To me, this seems to be the only sensible position. Acts of war are risky. They have big downsides. Sometimes, the upside compensates. Or sometimes there is no riskless alternative. But this looks like writing an at-the-money option, where you have nothing but down side and not much up side.