You hear anti-gay Christians quoting the Bible to justify anti-gay laws and practices, declaring homosexuality a sin forbidden by God. They say that they're not expressing popular opposition to homosexuality but speaking the unchanging word of God. But you don't hear them railing against the sin of having sex while a woman is menstruating. They don't call for schools to teach that menstrual sex is abnormal. They don't support the right to discriminate against people who practice menstrual sex. They don't call for laws against this behavior.
It's not as though the proscription of menstrual sex is a mere formality. Ezekiel refers to menstrual sex (but not homosexuality) to praise those who avoid it and condemn those who practice it.
"'But if a man is just, and does that which is lawful and right, and has not eaten upon the mountains, nor has lifted up his eyes to the idols of the house of Israel, nor has defiled his neighbor's wife, nor has come near to a menstruous woman, and has not oppressed any, but has restored to the debtor his pledge, has spoiled none by violence, has given his bread to the hungry, and has covered the naked with a garment; he that has not committed usury, nor has charged any interest, that has withdrawn his hand from iniquity, has executed true judgment between man and man, has walked in my statutes, and has kept my judgments, to deal truly; he is just, he shall surely live,' says the Lord YHWH."
Plenty of Christians will say that Jesus liberated us from the law, which is why we don't need to get circumcised and why we can eat shrimp. That's not a self-contradictory reading. The contradiction only shows up when Christians quote the Old Testament to condemn homosexuality but let heterosexuals slide on the menstrual sex deal.
So why do the Christians who rag on gays not also rag on heterosexuals who "uncover the fountain of blood"? Because they are expressing a popular prejudice rather than the unchanging word of God.
PS: Above Ezekiel is contradicting earlier scripture in which it is said that children suffer for the sins of their fathers to seven generations. Ezekiel, in this and nearby verses, is saying that YHWH metes out reward and punishment for what a man does, not what a one's father or forefathers have done. These verses also mention another forgotten sin—charging interest on loans. We don't hear much about that sin from Christian leaders these days, either.