Not at all. Evolutionists understand that humans, in the environment in which they evolved, that of the primate and that of the caveman, did not have the luxury of wasting their time and energy on immoral acts.
There is a principle in biology called "form equals function". Homsosexuality and promiscuity tend not to be traits that are favored. Sure, there are the occasional modern day isolated stone age tribes that engage in ritual homosexuality and favor promiscuity. But note that they are still in the stone age, and that fact indicates such behavior isn't evolutionarily positive. To suggest that evolutionists are a bunch of social nihilists and libertines is ludicrous.
Immorality and perversion is the result of settled civilizations, of people with the free time and material luxuries to contemplate performing such acts. It is social Darwinists that we need to be wary of - those who would advocate a society consciously decided to select out certain traits in a population.
It is what you never see them yelling about that gives away what they support. Evolutions never scream 'Abortion is wrong' in any significant numbers. In fact, I've never heard of one confirmed atheistic evolutionist attack abortion on demand.
I am not an atheist but here is an atheistic argument against abortion.
The average lifespan of a human being in the Western world is around 77 years old. A pregnancy only lasts 9 months. Because this life is the only chance we receive to experience consciousness, we should give every human being the opportunity to experience it. We are very good at asking people to make sacrifices destructive things for taxes, for material things, and for war. But we are hesitant to ask women to sacrifice 9 months in order to allow an individual to live 77 years.
Why should we defend the unborn to experience 'consciousness'? Who taught you that 'this life is the only chance to experience consciousness', such that it is something that is intrinsically good? And how was that larger goodness rationally justified?