His ancestors probably used the same humanist defense when enslaving Africans, who were looked upon as less-than-human: "It is not demonstrable that chaining Negroes is chaining persons."
Willful suspension of disbelief anyone? Talk about having no faith in modern science.
"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus