The best logical fallacy to give an atheist when discussing morals is to ask them why it's morally wrong to have intercourse with roadkill
It's dead it will not feel anything, nobody will know and there are no victims
If you ask a Christian or Buddhist why it's morally wrong, they will tell you it's because the body retains inherent dignity as part of God's creation (or the sacred flow of life), and desecrating it violates divine/natural order, harms your soul/karma, and shows disrespect, even if no one feels it or knows
An atheistic worldview of this question taken to its extreme, concludes that intercourse with roadkill is tantamount to masturbation and nothing more
