Last I checked, no one "qualifies" heterosexuality as parenting... and homosexuality isn't parenting, nor is it trying to "qualify" as parenting.How one on earth feels that homosexuality somehow qualifies as parenting is nuts, and perverted.
You don't "teach" people to be straight or gay, they just are. Parenting is about preparing your child to handle the challenges of life ahead of them and teaching them how to function in the world.
It seems you misunderstand the basic concept of parenting if you have to attach sexual orientation to it. There are homosexuals who are 10 times better parents than some heterosexuals, and heterosexuals that are 10 times better than homosexual parents.