story of racism? people find something offensive, if majority rejects it, result is we all have to put it as a "taboo" even though some of us dont' find it that bad.
incest seems wrong, to the majority, yet there's no reason that you can't advert easily.
Long story short.
90% of the human population (the morons) hate it, so it becomes illegal.
Plain and simple, fucking unfair :P
No offense, but basically from the two examples you gave, I can now assume you want to have sex with your family and you're racist. Congratz on being an individual!