HONG KONG—A TV show about a male love triangle is proving a big hit with viewers, but criticism from pro-Beijing politicians is stirring concern that broader freedoms could be caught up in China’s political crackdown, even as Hong Kong prepares to host the Gay Games in 2022.

“Ossan’s Love,” a 15-episode drama focusing on a romance among three men working in a real estate agency, has racked up hundreds of thousands of viewers over the past month. The show was praised by rights advocates for helping to bring gay relationships into the mainstream in Hong Kong.

But the locally made show also attracted high-profile detractors. Junius Ho, an outspoken pro-Beijing lawmaker, slammed the program as “marijuana coated in sugar” this week, suggesting it was harmful to society. Mr. Ho told reporters that promoting childless families violated not only traditional Chinese values and the three-child policy encouraging larger families, but also broke China’s national security law.

His remarks fanned concerns that politicians will use national security rhetoric—and a law imposed on Hong Kong last year to stifle political opposition—to push personal political agendas and target broader social rights in the city.

Several members of boy band Mirror, whose fans flocked to a promotional event in Hong Kong on Thursday, are featured in “Ossan’s Love.”

Several members of boy band Mirror, whose fans flocked to a promotional event in Hong Kong on Thursday, are featured in “Ossan’s Love.”

Photo: Vincent Yu/Associated Press

Carrie Lam, Hong Kong’s top local official, weighed into the debate, saying the show’s popularity didn’t indicate consensus in society for further LGBT rights in the city, where same-sex marriage remains banned. “This is still a very, very controversial issue,” she said at a news conference Tuesday.

Some rights advocates say progress made toward greater equality for LGBT people in recent years could stall or even be reversed as Hong Kong increasingly hews to the ways of mainland China, where feminists and gay rights advocates have been detained and social media accounts promoting such rights were recently removed.

Hong Kong was selected to host the Gay Games in November 2022, making it the first territory in Asia to hold the decades-old sporting event celebrating LGBT inclusion. The event is supported by some Hong Kong government bodies—including its equality watchdog, tourism board and an agency overseeing foreign direct investments.

The games, which will include dragon boat racing, trail running, performances and art exhibitions, are expected to draw 12,000 participants and 75,000 spectators from different countries, pumping an estimated $128 million into the city’s economy, organizers have said.

“How is it that we are hosting the Gay Games in 2022 and bringing into Hong Kong the attention and money, and yet we still don’t have legislation that protects LGBT people against discrimination?” said Michael Vidler, a public-interest lawyer who has litigated multiple LGBT rights cases in Hong Kong. “It’s just an extraordinary contradiction.”

Hong Kong decriminalized homosexuality in 1991 while it was a British colony, but doesn’t recognize same-sex marriage. Some recent court battles ruling in favor of same-sex couples seeking equal rights and benefits have been hailed by supporters as steps in the right direction.

Hong Kong’s mini-constitution, the Basic Law, guarantees equality before the law, Mr. Vidler said. There has been consistent progress in the courts recognizing LGBT rights over the past 15 years, thanks to individuals who took legal action against the government to enforce these rights, he said, “not because the administration has taken proactive steps.”

“Ossan’s Love” features actors Kenny Wong Tak-bun, left, and Edan Lui.

“Ossan’s Love” features actors Kenny Wong Tak-bun, left, and Edan Lui.

Photo: ViuTV

The international business community in Hong Kong has also thrown its support behind the cause, most prominently during a landmark trial that ultimately allowed foreigners in a same-sex union to be granted dependent visas in 2018. Multinational companies said such protections were needed to attract top talent to the Asian financial hub.

Jerome Yau, chief executive of local advocacy group Pink Alliance, said Mrs. Lam’s comments were at odds with research that shows growing support for LGBT rights. He cited a survey published last year by the Chinese University of Hong Kong that showed only 23% of the city’s respondents disagreed that same-sex couples should be allowed to marry, compared with 49% who agreed and 28% who were neutral.

Taiwan approved Asia’s first same-sex marriage law in 2019. In March, a Japanese court for the first time said the country’s ban on same-sex marriage was unconstitutional.

Lawmaker Mr. Ho said in a Friday interview with The Wall Street Journal that China’s national security law states that the government has a duty to carry forward traditional Chinese culture and prevent “unhealthy” influences from prevailing. Mr. Ho said he believed the Gay Games was the third episode of a “color revolution” in Hong Kong—following the 2014 pro-democracy Umbrella Movement and the 2019 antigovernment protests—this time with a “hidden agenda” to “promote the concept of not just homosexuality but same-sex marriage” in the city.

Hong Kong Chief Executive Carrie Lam said the show’s popularity didn’t indicate consensus in society for further LGBT rights in the city.

Hong Kong Chief Executive Carrie Lam said the show’s popularity didn’t indicate consensus in society for further LGBT rights in the city.

Photo: Vincent Yu/Associated Press

“Our aim for the event is to promote unity and inclusion, helping Hong Kong live up to its potential as a world-class city,” organizers of the city’s Gay Games said in a statement Friday. While the organizers applauded the advocacy work for LGBT equality in the courts, it wasn’t the event’s focus, the statement said. It added that Mrs. Lam had pledged her government’s support for the event on multiple occasions.

“Ossan’s Love” was adapted from a Japanese show of the same name and similar programs have drawn audiences from South Korea to Southeast Asia.

While the show has been praised for increasing visibility for gay people in Hong Kong, it has also received criticism that its central story line about a manager courting his subordinate offers a normalized depiction of sexual harassment in the workplace.

ViuTV, the Hong Kong broadcaster that produced and aired the series, declined to comment for this article. A representative of Mirror didn’t respond to a request for comment.

Excitement over the drama has rippled through Hong Kong’s younger generation. A kiss between the two main characters in the series generated local headlines. The pair—young men who are co-workers and roommates in a characteristically Hong Kong-size apartment—are played by members of the popular Hong Kong boy band Mirror. Their stardom has skyrocketed since the show premiered last month.

Some say Mirror’s popularity also showed a renewed affinity for local pop culture today. A Facebook group called “My wife married Mirror and left my marriage in ruins” has attracted more than 310,000 members.

Chelsea Ho, a 28-year-old Mirror fan, said that she and her friends watched the series with their families, which helped the older generation warm up to queer representation on TV.

“Is it the most realistic portrayal of LGBT society?” said Sherman Cheung, 28, a viewer who described the show as a milestone. “It may be a bit different, but the drama could help more people in Hong Kong accept them.”

Write to Elaine Yu at elaine.yu@wsj.com