One of the reasons the left promotes sexual libertinism is because of its tendency to expand government power. For example, unleashed homosexuality leads to more hate crimes (thought crimes) laws, more laws dictating who people can hire, who they can have as members of their private clubs, who they can sell or rent property to, etc. Gay marriage will lead to an expansion of social security, etc.
Promiscuity causes more illegitimacy, which means more welfare, more single moms voting for socialism, etc.
James Madison was right. An immoral people cannot remain free. Tocqueville was also right when he attributed America's greatness at least partly to our better morals than those found in Europe.
The more illegitimacy you have, the more often the state must be parent.