cpinva is correct that it starts in high school sports. It was used by some to try and intimidate. To be called a "fag" by someone meant that you had to fight. Period. To not fight meant that the person's place in the "pecking order" would be at the bottom and you risked being excluded from the group. That's a powerful lever on any teenager, even more so when a team association was involved.

But then, on gay rights issues I'll give it up for Disney, they've been at the fore for decades.  

There is rampant homophobia in the world of American Sport, of course.  It's a hyper insecure sub-culture in many ways, and very, very hyper-protective of an imagined intersect between hetero-masculinity and worth.  

Only one footballer (soccer player to you Yanks) has every come out as gay - Justin Fashanu.

  Tim Hardway's views on sexual orientation issues are similar to those one might find among countless guys sitting at some bar watching him play.

Not that they're crusading, or, preaching, or anything like that.  But all the talk shows and Sportscenter segments, as far as I've been able to tell, have been uniform in condemning Hardaway and those who would agree with him.  And the power of ESPN is considerable, its narrative reaches a staggering number of men (and not a few women), many of whom most certainly struggle with homophobic issues.  Perhaps it will benefit some of these unfortunates to see it framed in its true colors.  

It starts at a very young age.  When you are playing ball (all kinds) as you develop as an athelete you are constantly judged by your skill set, your attitude and your "heart".   All of this is defined roughly as your manliness.

The very essence of male compitition results in those who can't keep up being labled or singled out through jokes and peer pressure.  You are ranked by your skill level and those who are the most talented and successfull decide what goes on in a locker room and in the overall sports culture.

Someone mentioned that christianity plays a roll in the NBA.  That's only half the story.  The lifestlye of modern sports is a lifestyle most young men only dream about.  Road trips, booze, parties and groupies.  Read any book or watch a Real Sports special on it and you quickly learn that being a modern athelete gives you the opportunity to live the ultimate bachelor life.  All the money, women and fun a guy could want.   Hardly the environment condusive to openly gay men.  

  could the taboo against homosexuality be traced to a source similar to the taboo against eating pork and shellfish and other dietary "laws."

  In antiquity, the survival of "the tribe" was a far from secure thing. Behaviors which imperiled survival needed to be discouraged. People could grasp intuitively that certain behaviors such as eating things that for some unknown reason often caused fatal illnesses or not fathering as many children as possible in societies with very high infant mortality and very low life expectancies made the ultimate survival let alone growth of the tribe less likely. So, it was proclaimed that the Gods or God as the case may be forbid such things.

  My "sitting around revelation" was not as extreme. One year over the holidays a bunch of us from the old high school crowd were sitting around in someon'e parents' basement getting high when one the guys got all serious and and we got the dreaded "I want you to hear it from me before you hear it..."