I'm not a "fan" per se in that I don't find them particularly entertaining, but that really goes for most sports, from football to darts to porn: I enjoy playing them, but being a spectator sort of bores me?
In a really morbid way I would absolutely LOVE to see two humans at the peak of their physcal fitness / training go up against each other with absolutely no rules... just to know what that looks like. As it stands, even the MMA stuff with minimal rules does HAVE rules (obviously, as people would die) so it never feels quite... real enough...
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As for banning them, adults should be free to do what they want with their bodies so long as they aren't endangering anyone else who isn't consensually involved
