The context of his words is this (this is all from other Peterson videos): Marriage is not for you, it's for the children. Children do better on average when raised by both their biological parents compared to being raised by only one of the parents or with one of the parents and a step parent. Actually, a step parent is much more likely (100 times more likely if I'm remembering right) to abuse a child than a biological parent. He thinks sex is more serious than what people think nowadays. There is nothing casual about sex. Casual sex is not good for people, he says you pay a price for that. It's not good for you psychologically. Taking out of context something he said and using it to try to discredit him is standard behaviour for his opposers. I don't trust any article that doesn't link the full video or text from where they took his words.