It's fucked that people would lose their sponsors if they come out as gay.
It's a bit ridiculous, but there is still a subculture in America that hates anyone who isn't heterosexual and white.
I saw a bit of this growing up in a small white town, whose only diversity was migrant farm workers (who were not liked). The cultural norms that make this "acceptable" to some people exist in these little bubbles of people who haven't travelled, met new people, or seen bigger and better cultures. Not to mention the staunch religious practices of rural America.
But responding to your point - if a TM or company owner held these negative convictions, and a team member came out, it could end up badly for them. And that sucks.