Most people don't have any trouble following that one. This is laughably wrong and pretty insulting to women, who get plenty horny themselves and are no less capable of making their own decisions then men are. Casual sex is sex for pleasure, without the intention of building a strong and continuing emotional relationship. Callous sex is sex that uses your partner without considering the partner's rights, feelings, or consequences. These are not the same thing.
People having casual sex, if they're honest and kind, can be good for each other.
Sometimes, if they're lucky, that casual sex will become lovemaking. On the other hand, callous sex probably causes a significant fraction of the misery in this world. Note that this does not mean you have to believe you're in love every time you have sex. If there are no tender feelings on either side, the sex is likely to be mechanical and poor. If she has feelings about you that you don't about her, having sex with her is likely to leave her feeling unfulfilled and used, and can be cruel enough to leave emotional scars.