I think you're missing the point that antivirus should kick in before the malware executes. It's far from 100%, but if you download something stupid, the antivirus should in most cases flag that before you even have a chance to execute it. In that case, you delete it, and the problem is solved, no need to reinstall or anything of the kind.
Of course the "real" solution is to be smart about what you install, but no one is perfect and we also can't expect the world to be super computer literate (unfortunately).