In a notice posted on Friday, Weibo said it would be "cleaning up"content on the Twitter-like platform "in order to further create a healthy and harmonious community environment."
Among the targets of the campaign were "cartoons and short video content that are pornographic, promote bloody violence, homosexuality, etc.," the announcement said.
It said it had logged more than 56,000 items of content that "violated regulations," but didn't give figures for specific categories.
The announcement, which also called on users to report "illegal cartoons, games, and short video content," sparked a massive backlash from users, who protested using the hashtag #IAmGay.
“There's nothing wrong about being gay whatsoever," user @xingshi commented on Monday. "I am patriotic, helpful to others, and am no different to anyone else."
User @wandouhuanggua said "I support Sina Weibo cleaning up content related to pornography, gambling, and drugs ... but this can't be allowed to target the gay community like it did in the old days.
Suspicion and discrimination are wrong."
The company responded on Monday with a further announcement that it wouldn't be targeting "homosexual content."
"The clean-up campaign targeting games and cartoons won't be targeting homosexual content," the second statement said. "We are mainly looking to clean up pornographic and graphic violent content. Thanks to everyone for the debate and feedback."
'It pays to speak out'
Gay news account @tongzhizhisheng, or "The Comrade's Voice," said the "I am gay" hashtags had garnered more than 500 million views on Weibo over the past 48 hours, making it the most-read hashtag in China's internet history.
"Thanks to everyone who participated in speaking out," the account, which had previously closed itself down in protest at the move, said. "The Comrade's Voice account will be restarted with immediate effect!"
"It seems that it pays to speak out, because we got the attention of the higher-ups," user @yigebanxianshuo commented under the announcement. "Congratulations on your rebirth through death! We will continue to speak out."
Others said they want better recognition of LGBT rights across the board.
"I look forward to the day when same-sex marriage becomes legal in China and I will be able to say with pride that I fought to make it happen!" user @NansyLu added.
Last year, the authorities removed the lesbian app Rela and the gay dating app Zank from app stores, prompting some to wonder if the move was a part of state censorship of LBGT rights following a ruling in neighboring Taiwan paving the way for same-sex marriages.
The apps were accused at the time of failing to take responsibility for providing "safe content," official media reported.
Pressure to marry
Homosexuality was officially regarded as a mental illness in China until 2011, and LGBT people face huge social pressure to marry and have children.
China's state propaganda machine last year warned the country's tightly controlled media not to "make a big deal" of a May 26, 2017 ruling by Taiwan's constitutional court that effectively legalized same-sex marriages in two years' time.
Rights groups welcomed the landmark ruling, and called on other governments in the region to follow suit.
In April 2016, a court in the central Chinese province of Hunan rejected a complaint filed by a gay man against the government for refusing his application to marry his male partner.
Sun Wenlin, 26, had filed the historic complaint against the Furong district civil affairs bureau in Hunan's provincial capital Changsha, after officials from the bureau refused to allow him and his partner Hu Mingliang to register their marriage there.
Reported by Wu Jing and Kou Tianli for RFA's Mandarin Service.Translated and edited by Luisetta Mudie.