“That will never, ever, happen.”
Actually, it will. And already has, to some extent.
When the Civil Rights Act of 1964 was passed, there were a great many white people in this country who were racists. What happened to them? Many died off. Many evolved. And those who were left found themselves marginalized by the rest of society — to the point where even referring to someone as a “racist” was considered an insult tantamount to slander.
The same will happen to those who are anti-gay.