(CNN)Robbie Rogers has called for a change in attitudes after the world's first international study on homophobia in sport revealed widespread fear of discrimination.
Robbie Rogers wants change as study shows fear of homophobia in sport
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Rogers, who plays for MLS club LA Galaxy, is one of only a small number of openly gay professional athletes in world sport.
He said the findings of the Out on the Fields study showed a need for "change at all levels" after it revealed that 84 percent of those questioned -- including heterosexual men and women -- had witnessed or directly experienced homophobia.
They showed gay American men were the most likely to fear discrimination from coaches and officials in the six English-speaking countries -- also including the UK, Ireland, Canada, New Zealand and Australia -- researched.
"I was disappointed the study found so many people continue to experience and also fear discrimination," said Rogers, who came out as gay after leaving English club Leeds United in 2013.
"I hope this will start to motivate change at all levels. This change can start with every athlete or fan who decides not to use homophobic language, even if it's meant as humour.
"This kind of language is no longer acceptable -- everyone should be able to enjoy sport without fear of discrimination."
The 27-year-old urged governing bodies throughout world sport to "make committed and determined efforts" to ensure gay people feel welcome.
Out on the Fields questioned 9,494 people, including 2,064 Americans, on behalf of a coalition of groups including the Bingham Cup (the world cup of gay rugby) and the Federation of Gay Games.
It was released to mark the one-year anniversary of Michael Sam becoming the first openly gay player to be drafted to the NFL. Sam, 25, is currently without a club.
But although it showed that 83 percent of gay men and 63 percent of gay women under 22 had not come out to either all or some of their teammates, it concluded that young people playing sport in America were nevertheless more likely to come out than in previous years.
Mitch Eby, the first openly gay college football player in America, said: "I think the study has shown we are moving in the right direction with more people coming out in sport -- but there is still a long way to go and many changes left to be made."
He said he believed Sam "is not on an NFL team because he is gay. He is a good enough football player to be playing in the league," adding that "coaches or owners are reluctant, worried all the attention he might bring would be a distraction."
Brad Thorson, 27, a former Arizona Cardinals player, said: "I never allowed myself to entertain the thought of coming out as gay while playing football.
"In a large part, I think it's because homophobic language demeans gay men as weak and incapable, which I didn't relate to and didn't think it was possible to be a football player and be gay.
"The study has found there are a lot of gay men like me who are playing football and other sports and keeping their sexuality secret. I think sports will only change when more gay men decide to become more visible and get the support they need from coaches, teachers, officials and fans."
Pat Griffin of the University of Massachusetts, a pioneer of research into homophobia in sport, warned: "Although things are changing for the better and there is more acceptance overall, these athletes still fear discrimination. Unfortunately, Michael Sam's experience may reinforce these fears.
"However, I think we have a generation gap which reinforces the fears.
"Most straight team members are fine with having an LGB teammate -- but high school and college coaches, professional sport team owners and officials still have a way to go, and this may affect how athletes feel about coming out."