This is an excerpt from an NYT article. It's quite long, so follow the link for the whole story. It's an interesting read.
I asked Smith why he spent so much of his youth looking for trouble. I expected some sort of clichéd, though possibly true, explanation — a difficult childhood or a Napoleon complex. What I didn’t expect him to say was, “You know, bro, the sexual-preference thing.”

Smith is gay, and I know of no other professional fighter who is openly so. “I was always scared that my mom and dad would find out and wouldn’t like me, and my brothers wouldn’t like me,” he said. “I was petrified, because I didn’t want anyone to find out. And I would try to be the toughest person around. That way, no one would suspect, no one would ever say it, no one would think it.”
The gay issue is distilled on this gay site:
Shad Smith Becomes First Openly Gay Mixed Martial Arts Fighter
Article Date: 03/26/2008
By Dylan Vox

Mixed martial arts has become a national phenomenon, and with the creation of the Ultimate Fighting Championships, only continues to grow in popularity. This week, competitor Shad Smith became the first openly gay fighter in the sport when he revealed his sexuality in a New York Times interview.

According to the article, Smith entered his first fight in 2000 shortly after his release from prison where he was serving time for carjacking, one of his many stints.

He joined a more underground organization called Felony Fights, which has similar rules to the way UFC began in 1993.

Smith explained that he started fighting at an early age because of he was concerned about someone discovering his sexual orientation. "I was always scared that my mom and dad would find out and wouldn't like me, and my brothers wouldn't like me," he explained to the New York Times.

"I was petrified, because I didn't want anyone to find out. And I would try to be the toughest person around. That way, no one would suspect, no one would ever say it, no one would think it."

Now at 35, Smith has had several run-ins with the law, but is learning to settle down with his boyfriend Jesse.

Of his 20 fights, Smith has won 10 with 8 losses and 2 draws. Although he most likely will never make it to the Ultimate Fighting Championship, he explained to Nation writer Paul Wachter that he has learned a lot about himself from the sport.