There are two problems associated with substance abuse. Alcohol and drugs are dangerous because of the stupid things that happen while intoxicated. At least half of all spousal abuse is linked to alcohol abuse. Self control is part of life, it's part of growing up. Part of self-control includes avoiding things that can be additive.
Promiscuous sex can be addictive.
It can also be deadly. Sexual desires are even harder to control while intoxicated. It is also more dangerous because it risks the lives of unborn children. Substance abuse and free sex have a common philosophy. They both seek after self-induced pleasure.