Common decency says to tip and keep quiet. One should never make fun of mental illness
Common decency also dictates the person tipped or not tipped would just keep quiet as well. Also remember a tip is an option for proper service which appears to be in doubt.
Only one side of this story is posted, common decency would require both sides be presented before presuming what was the correct or incorrect action in this case.
Regardless of the truth the person who made the video absolutely intended to create hate by making it more about his mental disorder than about what actually happened. Which in of itself should cause a reasonable person to question why he posted as he did.