I guess I have to make an entire detailed post because you still don't understand.
It's not right to discriminate against someone for something they can't control. You shouldn't discriminate someone for being sexually attracted to their own gender, or to a family member, because that's something they can't help, they didn't choose to be sexually attracted to what they are attracted to.
However, discriminating against someone because they had *** with family member, while not necessarily wrong or right, isn't as bad as discriminating against someone who engages in homosexual acts. The reason for this is that acts of incest can result in a baby with harmful mutations. Homosexual acts don't cause any kind of inherent harm that is exclusive to homosexual acts, or any kind of harm that happens with homosexual acts vastly more than other *** acts like harmful mutations is with acts of incest.
You could say things like "Well what if two homosexual brothers have acts of incest, or two homosexual women, there is no baby, so no harmful mutations, so why is it wrong?" Well that's because we have evolved to avoid incest. We are evolved to embrace traits that help, and avoid traits that harm, and acts of incest cause harm, so we avoid it completely.