To convince your liberal gay friends they are wrong to be gay, tell them that being gay is the equivalent of being a racist. You explain it the following way.
Homosexuality is the same type of human limitation or defect that underlies racism. Gays and racists suffer from the same problem. Their problem is that when they focus on some characteristic of another person, for example the other person's race or sexual anatomy, and they find it different from what they are most familiar, namely themselves, they reject it. Their feelings of attraction are limited to things most similar to themselves. So as the racist rejects people of a different race, so too does the gay person reject people with a different sexual anatomy.
Of course, racism exhibits itself in the realm of general socialization, while homosexuality is exhibited in the realm of personal intimacy. But the principle is the same.
If a person believes being racist is wrong, then it follows that they should also believe being gay is wrong. And based on the same logic, they should find that advocating gay rights is morally equivalent to advocating policies that encourage racism or "racists rights".
So in reality, gay rights advocates celebrating their gayness are rather like white supremacists marching about and celebrating their rejection of non-white people. Both groups are celebrating the same principle of personal limitation through rejection of what is different. And both are missing out on the benefits of appreciating and experiencing natural human differences.
Then, after you tell your gay friends that being gay is the same as being racist and that advocating gay rights is the moral equivalent of encouraging racism, they will protest and make all sorts of counter arguments. You can respond to their counter arguments using the answers provided on this site.
