Agreed,. And if I didn't make it clear, I was in no way promoting or condoning consensual incest. But however distasteful it may be, it does exist - for example, one hears the occasional stories of couples who fell in love and later discovered they were first cousins, or siblings separated when infants.
Merriam-Webster defines incest as "sexual intercourse between persons so closely related that they are forbidden by law to marry[;]
also : the statutory crime of such a relationship". Nothing about abuse, psychological or otherwise. I just get annoyed when words acquire subtleties of meaning that can cloud intelligent discussion of the matters at hand. Consider "kill" versus "murder": it's almost never a good thing when someone kills another person, but that doesn't mean that all killings are murders.