I'm sure the snakes that he had for his testing were not pets. They were lab animals, bought for a specific reason. Also, I'm sure Diamondback Rattlesnakes are pets somewhere out there, granted they're not the same as Ball Pythons are with humans, they're still kept in a tank/tub under the care of a human.
I agree, it's crappy that he did this, but there are alot worse things that can happen. Just be happy that they were humanly euthanized at the end.