I found your question in Family and Relationships and went to your profile and found this one, as instructed. I think the reason you didn't get coherent answers is because you didn't phrase your question too clearly. What, exactly, IS the question? I think I know what you are asking, and so I will offer my two cents.
Sex, in a Darwinian sense, is a drive compelling behaviors that perpetuate the species. And, yes, people use this as an excuse to justify animal/cheating behaviors. But it is only the unintelligent that do this. The thinking man and woman do not use the fact that "sex is a drive that cannot be denied" to justify amoral behavior.
The dichotomy is in what social mores accept as "good" behavior, and this compelling urge to have sex that all of us share. Society wants monogamy and stable relationships so there is social stability and fewer anger/emotion driven murders and social upset, but the human animal enjoys lust. And I am afraid that it will ever be so.
So there you have it, if my perception of what you are asking is correct. The stupid people have indiscriminate sex. The intelligent/educated do not. Or at least they are not supposed to.
What are you gonna do? We all like sex, right?