This was on the Huff Post:
"Richardson again apologized for saying last week he believes homosexuality is a lifestyle choice rather than a biological characteristic. The comment at a candidates' forum on gay issues sparked outrage in the gay community.
"I made a mistake. I screwed up," he said, acknowledging that the gay blogosphere is upset with him."
That's a touchy subject. But I think what he's referring to is that it's easier for someone to choose to be Gay or hide that they are. For decades prior to the 20th Century many Gay entertainers had to hide -- be in the closet -- rather than reveal who they are. Many even got married.
My take is the people who were attacking him were undoubtedly too young to know this.