Bodybuilding must be the biggest gay sport there is. That is, it attracts the gay crowd as the biggest supporters there is. Whether the bodybuilders themselves are gay is open to question.
But there is some connection to the gay life style, such as admiration of the male body, frequent preening in front of the mirror, an obsession about one's looks, wearing tight and colorful briefs (and G-strings, pouches, posing straps, etc.), shaving one's body, going to extremes or excess by overdeveloping the body, etc. These are what gay men do, and so do bodybuilders.
Joe Weider and Bob Hoffman, the two gurus who promoted bodybuilding contests, continued a hateful rivalry that didn't reflect well on bodybuilding. Weider admitted bodybuilding attracted gays, but he said the bodybuilders themselves weren't gay. (Ahem) Hoffman accused Weider of publishing gay magazines (Body Beautiful, Adonis, Young Physique, etc.) and said he was getting out of the contest business because they were "sissified things." And he denounced Weider for trying to produce "monsters."
A psychologist who appeared on The Mike Douglas Show, which I did not see but read about, after an appearance by Steve Michalik said something to the effect that "bodybuilders are immature individuals who have to overcompensate in order to mask deep-seated insecurities." Hmmmmm.
I recently read a book on Groucho Marx in which Mae West is quoted as saying, "The musclemen in my nightclub act? They were all homos. Oh, what a waste of manpower that was."