Queer by choice people want to have our marriages legally recognized just as much as other queer people do. Many of us live in jurisdictions that do not recognize our marriages. (For example, the owner of this website, Gayle Madwin, is engaged to be married and lives in California.) There is no reason that fighting for our legal right to have our marriages treated equally should involve feeling pressured to lie about our experiences of choosing to be queer.
In 1948, the California Supreme Court was the first in the U.S. to legalize interracial marriage. By 1958, a Gallup poll found that 96% of Americans still disapproved of interracial marriage. If majority vote had been allowed to overturn the court decisions, interracial marriage might still be illegal today.
Many of the people who opposed interracial marriage cited biblical justifications and argued that, after all, people have a choice about whether to date someone of another race. No one is born a member of an interracial couple. But the courts (including both the California Supreme Court in Perez v. Sharp, 1948, and the U.S. Supreme Court in Loving v. Virginia, 1967) have consistently found that banning interracial marriage discriminated on the basis of immutable characteristics, because each member of an interracial couple was born with his or her race, and it is not reasonable to imagine that couples who love each other and want to marry each other would feel free to just dump each other and go marry people of their own races.
In exactly the same way, each member of a typical same-sex couple was born with his or her gender. It is ridiculous to argue that if we want equal rights, we can just divorce our spouses and go find ourselves new spouses of a more politically advantageous gender. No one who loves their spouse could ever do that. Any people who think we should are revealing how thoroughly they are the ones devaluing marriage.
It would be irrelevant and insulting to go looking for an "interracialsexual" gene that makes certain people incapable of being attracted to members of their own race, just as it would be irrelevant and insulting to question whether members of interracial couples have had some sort of bad experience with members of their own race that drove them into the arms of a member of a different race. Instead we assume, quite rightly, that it is perfectly normal for all people to be capable of attraction to members of any race, even though not everyone actually experiences it or ever becomes a member of an interracial couple. Same-sex attraction should be seen the same way.
Different people have different opinions or experiences about the extent to which falling in love with particular people is a choice for them, but none of these can ever justify depriving us of marriage licenses. The people who try to tear our families apart inevitably tear their own families apart along with ours. The odds are very high that if you vote to ban same-sex marriage, you will sooner or later find that a child or grandchild or niece or nephew of yours is in love with a member of the same sex and has concluded, remembering your effort to ban same-sex marriage, that you are a bigot who does not love them.