I agree to an extent, but it's not so simple. I'm-just-trolling is the modern equivalent to I'm-just-kidding; you have to reasonably assume that someone using a cheap out from a poorly formed argument is either a terrible comedian or generally spineless in his convictions. In either case, it would be inappropriate to pursue someone for a statement they are unwilling to seriously defend. Calling someone out for backpedaling is one thing, calling them out for believing something even though they're recanting in a cowardly way is another.