We have legislation defending and protecting animals lives as well. Some states have the death penalty, so obviously not every humans life is defended by legislation.

And we don't really cull wild animals. Unless you're arguing that hunting is wrong..? We generally don't wipe out an entire population of animals. Generally we try to relocate them or control their population levels. You might be referring to invasive species, and in that case we are attempting to kill off an entire species but only because they will destroy the environment they are in and it's more detrimental to leave them alive than it would be to kill them.

And I would consider chopping up a baby and selling the body parts and stem cells to be torture. Call me crazy though.