Would be anti-gay rights legislators: a question?

It isn't "the Old Testament" that no longer applies! It is the tenets of the Mosaic Law. Basic moral teaching never changes. The Ten Commandments are from the Old Testament, but they apply until the end of time. Such basic moral teaching is the same, Old Testament or New, which is why it is not necessary to quote Leviticus on acts. The New Testament likewise condemns such behavior. 1 Cor 6:9, 1 Tim 1:10