Argument: Religion should have no role in incest law
"Inbred obscurity: improving incest laws in the shadow of the "sexual family". Harvard Law Review. June 2006 - "Religion also does not provide a viable rationale for incest prohibitions. Based on current Establishment Clause doctrine, a predominant religious purpose would render incest prohibitions constitutionally invalid, 33 especially because those prohibitions trench on constitutionally protected activities such as marriage and sexual intimacy.34"