There have been a number of things photographed and videoed by military folks posted on the innernetz that have caused a lot of controversy. My military experience only put me in "harm's way" very briefly. From what I've been told and read, I can only barely imagine the stress these folks are under.
My impression of that stress causes me to think I somewhat understand their need to relieve the pressure. Their relief is often found in humor. At and among themselves, their situations and their living conditions. This video is just a minute, 33 secs. I had to stop and replay in a couple of spots so I could "get" the humor.
If you'll go to YouTube and type Military Humor in the search box, you'll find hours and hours of clips.