I'm talking about two adults...say a Father and daughter. Should their sexual behavior be legitimized and accepted because it is between two consenting adults? Yes or no?
I was mistaken in my earlier post. Sex between consenting adults who are closely related is a felony in at least a couple of states: Alabama and Missouri.
Here is site with a survey of sex laws: http://www.geocities.com/CapitolHill/2269/
Of course, different jurisdictions define incest differently, whether the law be crimimal or civil. Some states include cousins, others do not. Some include adopted persons.