I'm not completely sure that we should. Appropriate and undoubtable retaliation for wrongs is one thing, but busting heads to persuade them to be more "democratic" ain't going to work.
It worked fairly well for the Germans and Japanese. Of course, they had a history of civilization and learning. So I don’t think it will work in Afghanistan, just pointing out that “busting heads to persuade them to be more ‘democratic’” has worked in the past.
Who said anything about being democratic?
Democracy is a really, really bad idea - our own field manuals said so until the 1930s (Hmmm... I wonder what changed?). Even Representative Republics are hard to do - look at what is happening to ours.
Folks like Afghanis, Iraqis, Syrians, Egyptians, etc. need authoritarian governments that can, and WILL bust heads if the herd gets out of line. They also need leaders who can pull an orderly transfer of power even in the face of civil unrest. What they don’t need is “democracy.”