Dark Knight Returns began as a possible future in the '80s, now it's a separate Earth. Of course it's a different Batman, Superman, etc. then the New Earth versions in the regular titles, thankfully. I prefer the DKU versions with no Damian, no Dick Grayson as Batman, no Batman stuck in the prehistoric caveman era, no Catwoman with a baby, no New Krypton, etc.
His thoughts are accurate expressions of his true feelings. If Bruce Wayne was gay, he would, with 70 years of comics, have "let slip" his orientation in his thoughts. He would have questioned what he was doing with all those women, Julie Madison, Catwoman, Linda Page, Linda Lewis, Queenie, Vicki Vale, Batwoman, Tala, Silver St. Cloud, Julia Pennyworth, Natalia Knight aka Nocturna, Rachel Caspian, Shondra Kinsolving, Vasper Fairchild, Sasha Bordeaux, Jezebel Jet, and that it was all some big lie. No one is truly confused about their sexuality as late as college age. Batman didn't need to be changed to not look homosexual. He was shown to be attracted to women since the beginning, Julie Madison, Catwoman, Linda Page, Linda Lewis, Queenie. While Fredric Wortham was attacking comic books in his 1954 book Seduction of the Innocent calling Batman a homosexual Batman was shown to be attracted to Vicki Vale. On the Adam West Batman television show and spinoff movie Bruce Wayne was shown to be attracted to Molly, Lisa Carson and Miss Kitka/Catwoman. "Catwoman, you give me curious stirrings in my utility belt."
We are born already "programmed" for our sexual preferences. Over the course of our lives, we may learn techniques beyond what Mother Nature provides, but the strongest evidence indicates that no one "learns" to be a homosexual unless the matrix is already imprinted in their brains. Homosexuality is not a "choice". Homosexuality comes from within, from the DNA of the individual. And of course there is nothing wrong with people that are gay.
Homophobes don't believe that homosexuals are born that way, they think that straight people can turn gay and that gay people can turn straight. Being a homosexual is not something someone can "catch". It's not a virus or bacteria that causes someone to be a homosexual. One does not wake up one morning thinking "Gosh, I think I'm turning gay now."