Sporting Event / Competition
Because of the appearance of metahuman athletes, debates about the qualifications for Olympic competitors having a "extreme genetic advantage". Should people born with particularly athletic genes be allowed to compete? What about those who, through no fault of their own, became mutates? Is that any different from athletes whose trainers provide them with chemical boosts of a non-mutagenic nature? Where does the Olympic Committee draw the line?
While technically, a naturally-born mutant is considered a valid candidate according to the current Olympic guidelines, such a strong stigma against metahuman competitors is present to this day that few are willing to subject themselves to the genetic tests and background scrutiny involved.
All of this process took so long that the Summer Olympics were delayed from their scheduled 1948 London, England event to happen in 1950 instead. Winter events still happen according to the original schedule, but all subsequent Summer Olympic events are on a two year delay.