The top-trending hashtag "Sun Yang Don't Cry" amassed more than 47 million views on China's Twitter-like Weibo within hours, Fairfax media reports.
Fans on social media as well as reports on popular Chinese online news portals including Sina and Tencent described the Australian's "drug cheat" comments as classless "taunts" and slammed him for rubbing it in after winning.
Chinese fans have also bombarded Horton's Facebook and Twitter accounts, demanding he apologise to Sun.
Horton's post-race celebratory Instagram photo was flooded with comments from Chinese fans, with some calling the Aussie a "snake".
"Although you have to the gold medal, but no matter how much you get the piece because of your character you will always be a loser at least respect you should have! Please apologize to Sun Yang! [sic]," one user wrote.
"Good for you to win the game! But please figure out the truth before you speak bad things about others," another commented.
Yang served a three-month ban for testing positive to trimetazidine, a substance normally used to treat angina.
Yang claimed the medication was prescribed for heart palpitations, saying he was unaware it had been placed on the banned list.
- AAP