Incidents like these indicate tit-for-tat responses to similarly deplorable acts from the enemy like making footage of beheading of people by Taliban and similar acts. Guilty personal of both sides should be condemned for engaging in such inhumane activities.
Member Jihad also raised some relevant points. The horrors of wars can leave a psychological impression on any human involved. Humans are not drones.
In addition, soldiers can take some liberty at making fun of the 'bad guys' on a few occasions with the assumption that they will not face scrutiny on the basis of disgracing the 'bad guys' because they are already doing the 'good job' for their country and those whom they are helping.
However, I believe that US administration should give instructions to all of its military personal to avoid doing this kind of stuff at any cost due to the sensitivity of these matters. These incidents reflect poorly on the image of ISAF in the global scenario.