I still think that humans respecting similar creatures not really stems from evolution.(but rather psychology) When we respect creatures like that, we do not do that at the same level other creatures do, most of our evolutions past we could not respect them in that sense, because our brains were not developed.

To think some aspect of a creature is the way it is because of evolution does not only require it to be positive for the genotype. There must also be a way that the selective process that advantages that genotype. Respecting similar creature would require a selective process on a set of creatures so large that it can not really be taken as causal.
(btw do not feel like i am clear enough here)