As I understand it, once you have already joined a guerilla organization like the Taliban, you have generally made peace with the fact that the drones are there. Watching someone die by hellfire missile strike further confirms that the evil people who are oppressing you by drone need to be stopped. Also, showing other people the aftermath of a strike helps to convince them to support you because they think they might get caught in the friendly fire.

It's a little like surrounding an army on an open field: If you give the losing side in a pitched battle an escape route, many of them will run, but if you surround them, they will fight to the death because there's nothing else they can do.