So I don't particularly feel like watching an entire hour-long video about something I'm already very familiar with for the sake of an argument on the internet; I'm just going to skim the video and look at the slides.

He describes monads as "a loophole" in the idea of function purity. This isn't true; monads aren't a way to 'cheat' any more than passing an accumulator through like

  factorial acc 1 = acc
  factorial acc n = factorial (acc * n) (n - 1)

is. He says something about state and functions and closures that I can't understand and how the state is 'always different', and it's just nonsense as far as I can tell.

He also calls values 'monads', which isn't accurate terminology at all; they're usually called monadic actions.