When you order a soldier to commit a war crime he might refuse. A machine never refuses.

This. Also a machine doesn't come back with PTSD, wounded or in a coffin, so there are no parents, relatives and friends finally realizing the true costs of war.

Of course some crimes are committed by soldiers who are actively disobeying orders. An autonomous weapon is not going to feel any of the emotions that lead soldiers to do terrible things.

He might but humans have this amazing track record of slaughtering each other. Recently (1990s) with machetes in Rwanda. Very low tech.

I don't trust humans to avoid war crimes. Robots could have protections built in in a way that international orgs can verify.

Those international orgs are run by humans.

So what?

Is a gun unethical for having a trigger that never 'refuses' to shoot? And on the other side of that argument, machines lower the risk of atrocities like the rape Nanjing to zero.

The flip side of this argument is that an effective army needs people who to a large degree don't refuse orders.

They aren’t. Conventional weapons manufacturers don’t have a great cool factor. See Masters of War by Bob Dylan for a popular take on this.