By breaking up "Love" and "Sex" into two distinct Themes, we're not saying that Ovid thinks they don't mix (even though, if you read through the poem, there are surprisingly few couples who enjoy an active sex life and a healthy, loving relationship). What we are saying is that Ovid sees them as distinct experiences: couples can be deeply in love (like Deucalion and Pyrrha, or the elderly Baucis and Philemon) without us hearing a peep about their sex life, and people can be consumed by sexual desire without feeling the slightest tinge of human emotion for the other person. This points to the dangerous side of sex that appears repeatedly in The Metamorphoses. All too often, the uncontrolled sexual desire of Ovid's characters (usually, but not always gods) can make them pursue partners aggressively, often through rape. Even when sexual desire is not negative in this way, it is still represented as an overpowering force.
Ovid portrays uncontrolled sexuality as dangerous.
Ovid portrays men and women as equally susceptible to sexual desire.