Short answer it is restomping the groin.
TORTURE PORN definition: a genre of horror films in which sadistic violence or torture is a central aspect of the plot See examples of torture porn used in a sentence.
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So self defence invent this idea that there are these bad guys that are ultra violent but also incompetent. Creating this scenario where you can justify using the baddest of moves but also so crap that these moves will work for your average soccer mum.
I assume it to convince people they are powerful without ever having to learn how to fight.