If there were to be discovered, through DNA studies, that being born gay, was a natural thing in humans & there was a way to scientifically engineer the DNA to stop this from occurring, Do you think Christians & the ilk would do it? & if they did would they be going against God's plan?
The Christians I've encountered would not believe or accept the scientific studies you described. Also expect to hear claims that there would be negative consequences from tampering with God's plan.
That's why they're so determined to believe that homosexuality is chosen.
Because if the acknowlege that it's inborn, then homosexuality has to be part of God's plan. They'll never admit that, if they can help it.
They would say that God is testing the Homosexual, and God never gives you a test you can't pass.
Then they would burn you like a witch.