Jan,
Excellent points. I still remember (and thank you) for private emails correcting me about my use of this fallacy.
Emyrose,
>But aren't all ethics or moral values a matter of preferences rather than logical conclusions?
Not always. Pedophilia causes great harm to children, so logically we can conclude that pedophilia is unethical and immoral. The same can be said about incest, genocide, etc.
Some moral values such as condemning fornication may have made sense in the past; it prevented single women from having to raise a child. However, today with birth control, suitable protection, and women's rights, it makes little sense to completely condemn fornication today. I am not saying everyone should fornicate, just that a blanket condemnation does not make sense.
Adultery is another "sin" that logically cannot be made a sin under all circumstances.
>Thus, we could never condemn homosexuality with logical arguments.
True. I have yet to see a good argument against homosexuality.
Richard