wasn't around for the slaughtering of the buffalo. Nor have I ever seen a Passenger Pigeon, and I don't think these animals were killed in the "name of God"
That is not quite correct, Juan. I have read somewhere that white man decided to kill the animals (buffalo, bears, wolves etc.) precisely in the name of God. Their aim was to evangelize the Indians. Indians regarded many of these animals (wolves, bears etc) as holy, as sacred.
White man’s argument was that if he can kill off the animals, he can prove to the Indian that his Gods were the weak Gods (since they could not prevent the slaughter), that Jesus was the stronger God (since he was able to destroy the holy icons of the Indians), and will decide to embrace the stronger religion, the only true religion, Christianity.
The wholesale slaughter of the animals that white man embarked upon can be explained at least party by reference to Christian God.