I think society as a whole determines what is acceptable, not acceptable and illegal. Incest is hazardous for procreating as we all know. We really do not know what the psychological effects may be as it could very well be different for every one right up to darn right damaging.

As for the attraction, that's nothing new. Mothers and sons is not as common as father and daughters but IMHO equally damaging on a psychological level at the very least. I think it's purely sexual perversion for the most part. But of course 20 years ago gays were taboo and 50 years ago interracial marriages were taboo. I don't think society as a whole will ever accept incest or pedophilia. I'm not judging, just stating my humble opinion.