I'm afraid he will.
He boxed himself in with his ill-advised "red line" comments. Plus the "I've never met a war I didn't like" crowd in Congress, led by John McCain and funded by the arms merchants, is continuing the pressure on him to shoot, along with Israel of course.
And, morally, a measured reaction is probably justified. The problem is that it's always the US that is forced to do the shooting. The consequences, as you say, are the people in the Arab street who will continue to be outraged by the inevitable "collateral damage" which will be caused by Assad's setting up refugee camps next to military targets. I haven't seen news that he's done this yet, just conjecturing. . .
Care to bet against it?