These things do occur in real life. Granted I don't foresee a professor showing a beheading video in class. However, for the sake of discussion, if the class is about geopolitical theory/issues and the discussion is regarding how do we deal with terrorists. Maybe the student believes we should treat them with peace and love but has actually never dealt with this issue in real life. By all means show them a beheading video without warning to see how their opinion immediately changes.
People used to congregate for miles around to watch a good beheading. They sold beer and pastries, and people fought to dip their handkerchief in the blood of the executed. It was a grand entertainment.
Now we watch Bachelor in Paradise. I'm not sure it's an advancement.