Yang served a three-month suspension in 2014 after testing positive to a banned substance.
After the race, Horton said, ‘I used the word “drug cheat” because he tested positive,’ Horton told reporters. ‘I just have a problem with him testing positive and still competing.’
However, Fairfax Media reports Horton’s comments were part of ‘a deliberate ploy to get in the head of his main rival.’
In response, Yang said: ‘I don't care too much what the Australian athlete says ... I'm clean; I've done everything it takes to prove I'm clean.’
Yang might not care but his supporters certainly do, starting the hashtag #apologizetosunyan.
‘You even won the match, but you are still a loser, you don't deserve to have an Olympic gold medal,' wrote one person on Instagram.
Another wrote: 'You are too complacent and will die quickly.' Others have spammed the champion’s account with snake emojis.
Following the abuse, the comments on all Horton’s photos have since been deleted, possibly as a result of Instagram’s new filter that blocks aggressive comments.