Perhaps emboldened by Horton, American swimmer Lilly King attacked her chief rival in the 100m breaststroke, Yuliya Efimova. King, 19, initially wagged her finger at Efimova then baldly stated: "You've been caught drug cheating... I'm not a fan."
Efimova has few fans outside her family and Russian network, and was roundly booed by the crowd. She has twice tested positive for banned substances and was only cleared to swim at the Olympics this week. Quite how Fina, world's swimming tsars, came to that decision is anybody's guess, but this is the sort of nonsense that the IOC's abrogation of responsibility has encouraged.
Lilly King today defeated Efimova in the final in a race that was billed as Good v Evil. This is great for sound bites and headlines, but sad for sport.
King went even further, saying her compatriots Justin Gatlin and Tyson Gay should not be in Rio either.
"No, do I think people who have been caught doping should be on the team? They shouldn't. It is unfortunate we have to see that," she bravely said.
Think about that for a second - a 19-year-old is providing the sort of ethical compass lacking in administrators.
Instead of the sport's administrators taking a stand, the athletes are taking matters into their own mouths. It has the potential to get messy.
There is another side to this outrage and suspicion though.
On day one, Hungary's Katinka Hosszu swam the most remarkable medley in history, shattering the world record by close to 2.5s. On day two, Katie Ledecky swam the most remarkable 400m freestyle race in history, smashing the world record by close to 2s.
Guess which swimmer has been the subject of the most suspicious smears? A clue: it is not the golden child from Stanford University.
We in the nebulous West have been conditioned to think the worst of athletes from the near and far East.
We tend to forget that their have been plenty of dirty athletes from all walks of life. If you have any doubts, read Richard Moore's The Dirtiest Race in History: Ben Johnson, Carl Lewis and the 1988 Olympic 100 Final. Read any recent history of the Tour de France for good measure, too.
Working on broad generalisations, the fundamental difference is that Western doping has traditionally been a private enterprise, while there is a mountain of evidence to suggest doping has been systemic in the East.
This much was proven when Russia's elaborate doping programme was exposed. This should have been the tipping point. The time for the IOC and its member nations to take the strongest stand.
Instead they left it to the sports, who didn't have the stomach for the fight. In the saddest example of the trickle-down effect, they in turn have left it to the athletes to make a stand.
Like it or not, Horton and King have shown the kind of fortitude sport's most pampered executives lacked.
NB. This column was updated to include Lilly King's latest anti-doping comments.