Boxing i never count as sport. Corrupted rankings to prevent fighter xy to get a championship fight, fixed outcomes en masse, 5 different associations with 20+ fighting classes (actually there must be around 100 current "world champions", what a joke), at best doubtful doping controls, and so on...
P.S.: And even if we block out my above mentioned points (which lead to bogus results), the above mentioned boxers showed their talent early. Something completely missing with Horner.
The excusers have to face and accept the truth: Horners performance is unprecedented in the history of sports. And if there was something grotesque as his performance, those were caught (Michelle Smith comes to mind).