So what happened before the start of the video? The old man was conversing too loudly on the fone and the young guy tried to quiet him down and then the occurences in the video began?
From the scene of the video alone, it seems the old guy stepped overboard. Lecturing on the young man about some manners is okay, but bringing in disrepect to his mother in that form is totally unacceptable. If the young man had a been a gang member or somebody a bit more volatile, the old bugger coulda ended as a statistic.
Also, talking loudly in public places like public transit is indeed frowned upon, here at least. One time, a girl was very loud on her cell phone and the entire bus ended up staring at her.