Why Do 11% of LGBT People Oppose Same-Sex Marriage?

According to a new report on LGBT issues from the Public Religion Research Institute: "LGBT Americans overwhelmingly support same-sex marriage. Close to 9-in-10 (86%) LGBT people support allowing gay and lesbian couples to legally marry, while 11% are opposed."

Who are these lgbt people who are opposed to same-sex marriage!?!?!?! Because, the thing about gayness is that it is an identity that you yourself take on, consciously and purposefully, every single time. You "come out". In order for the PRRI to count you as part of LGBT Americans, they have to say "are you LGBT?" and you say, "yes". So this doesn't include men who have sex with men or women who have sex with women, and identify as straight. This doesn't include "ex-gays". This doesn't include people who have desired members of the same sex their whole life, but do not call themselves gay or bi.

I do not understand how you can identify as gay, and then oppose your own right to get married. I understand thinking, "I don't support the push for same-sex marriage, because I think those funds should go to HIV prevention, and marriage is an oppressive institution anyway, but yeah, if there was a ballot tomorrow asking if my state should define marriage as between one man and one woman, I'd vote no." But not this. Isn't coming out in large part about saying, "look, whatever internal wrestling I've done over this, that's in the past, and I've decided to accept myself for who I am"? And I am genuinely asking - I wasn't raised in a particularly homophobic environment (my mom identifies as "a fag-hag, before we weren't supposed to say that word anymore", and my parents reacted to me coming out with about the same reaction as if I'd announced I was going to the library the next day), so I have trouble relating to a lot of the stories about shame and self-hatred over one's sexual orientation that so many lgbt people have. But, I just really do not get this. I have trouble understanding there being 20 lgbt people who opposed same-sex marriage, much less 11% of the entire community.

ETA: The question asked was: ""Now, I'd like to get your views on some issues that are being discussed in the country today. All in all, do you strongly favor, favor, oppose, or strongly oppose allowing gay and lesbian couples to marry legally?"