He really says that. He really makes threats against the guys life which are recorded on camera and can (and should) be used against him in the proper channels. The issue here is not really showing up with a fake M but one idiot trying to assert himself in a quintessential thug manner over another. It's your basic bro down although on a different level as with people standing around watching the show the guy is posing like a thug yelling and screaming for maximum effect. It's a shame the smaller guy doesn't stand up for himself and is not prepared to defend himself.
Regardless, this is a lesson in not taking online problems offline and always keeping in mind you do not know who is behind the computer screen. You also do not know who you will run into at an offline meet. Always be prepared, always protect yourself. Especially if someone tries to damage your property as what happens in the video.