I allow my mind to wander sometimes (particularly on the bus) and somehow wound up thinking about incest. I get that it's wrong, The thought of being sexual with my brother is definitely not appealing, but I don't get why.
What are some objections to incest?
The two I can think of is genetic diversity is compromised in cases of reproduction from incest, and psychologically it may not be healthy.
The genetics argument is essentially invalid due to the availability of contraception, abortions, and the fact that there are over 7 billion people on the planet.
The psychology argument would be valid if shown to be true, although even then it should be treated as a psychological problem, not a criminal one.