The military is like an organized play. Everyone who assumes a position is supposed to follow the script to their role. However, some take it too far and continue even after the play has ended. These folks are always in character and they expect the same out of everyone around them.
In the field it's understandable but if one of these "motards" pulls rank on you during liberty, you may be inclined to react the same way this Marine does.
Watch (some profanity):
NOW: This hilarious video shows the 'hype vs. reality' of Marine life
OR: Here's the way-funnier version of what the Marine PFT is really like