Horton, Australia's delegate in swimming and won the gold medal during the 400m freestyle event at the Rio Olympics last week. Sun Yang, China's swimmer, finished with a silver.
After claiming his victory, Horton commented to the press that he "had no time or respect over drug cheats" in the context of Sun Yang's three-month suspension after testing positive to a drug test.
The Chinese athlete tested positive with the drug trimetazidine. Sun claimed that he uses the drug to manage his chest palpitations and was unaware that the drug was placed on the banned list.
Netizens were outraged by the comment and flooded Horton's Twitter, Instagram and Facebook accounts, demanding that the athlete apologize to Sun.
In Sina Weibo, the hashtag "Horton apologize to Sun Yang" has already 69 million views. Chen Ou, Jumei CEO, took one step further and said on his Weibo account that he will give discounts to users who use foul language against Horton.
The Chinese Swimming Association demanded an apology from the Australian Swimming Association because of Horton's personal attack. The Chinese said that Horton "damaged the relationship between both countries' swimming associations."
Sun told Chinese media, "That is just the gimmick of the Aussie swimmer. Every athlete in the Olympic Games is supposed to be respected."
However, there are others who think that the Chinese should not be too sensitive.
Yang Zao, a research fellow at the Chinese Academy of Social Sciences, said, "Chinese people are too sensitive, and we can't take everything to a patriotic level and ask others to apologize when individual Chinese have disputes with the outside world."
The chief executive of Swimming Australia, Mark Anderson, said that they fully support Horton's comments.
He said, "We do support our athletes and trust them that when they say things, they say them with respect and openness and transparency. Mack made that statement and we absolutely back it."