Over 200 teachers and parents have issued an open letter calling on society to protect sexologists' and sex educators' work and condemn physical and verbal attacks on sexologists.

According to a letter titled "Say no to behavior disturbing sex education" published by the China White Ribbon Volunteer Network on Friday, an organization promoting sex education in schools, attacks and slanders against sexologists and sex education volunteers have been common of late.

A total of 261 supporters including parents, teachers and sex education volunteers signed the letter, and appealed to the public security authority to punish those attackers.

"Besides the public security authority, we also appeal to websites and Internet management departments to delete related posts and punish the posters," the letter reads.

"The controversy of whether we should introduce sex education to students will continue for a long time, and we respect that people have different opinions on it," Fang Gang, a sexologist from Beijing Forestry University and the founder of the network, told the Global Times.

But opponents cannot smear or attack those who hold different opinions, or try to force others to accept their choice, Fang said.

Several sexologists including Fang were attacked in 2014 during their promotion of sex education. Peng Xiaohui, a sexology professor with Central China Normal University, had a bag of feces thrown at him by a middle-aged woman at a sex culture expo in Guangzhou. Several people denounced Fang and demanded his university dismiss him in anonymous letters last year.

Fang said that some parents opposed sex education because they feared their children would practice sex or do something bad after they learned it.

"But sex education is aimed at letting students have a correct understanding on sex-related issues rather than pushing them into having sex," Fang said.

As China has no unified textbooks on sex education, Fang created a textbook for high school teachers this February, which covers a variety of topics ranging from love and sex to gender equality. 

Wen Xueqi, a psychology teacher from Shandong Experimental High School in Ji'nan, said that he only teaches sex education in two lectures to grade one students in his school.

"My lectures only cover basic knowledge, such as relationships," Wen told the Global Times.

"Topics like masturbation are only discussed when students ask," he added, noting sex education could reduce unwanted pregnancies and abortions.