[T]he first question of ethics is why do I not kill you and take your stuff.
The ritual of setting aside this question in order to enter into debate has been lost through the ages. And common interest conveniently assumed as the starting point, rather than the necessity of choice between cooperation, parasitism, and predation. If we assume cooperation this is a fallacy. Cooperation itself must be valued higher than non-cooperation.
Instead, why do I not kill you? What are the minimum criterion for cooperation under which not-killing you is advantageous?
Certainly it is not rational to permit violence or theft. Certainly not deceit. Certainly not the imposition of costs. Certainly not danger to my kith and kin.
Certainly not at an expense to my kith and kin (( Literally, albeit archaically, friends (“kith”) and family (“kin”). )).