People are weird; myself included.
The same person who rants about the inhuman treatment of an unexpectedly gifted goldfish will routinely ignore the fact that the fish they bought are part of a process which results in the death of thousands of fish every day. Or they'll excuse the death of a new species in their tank as an unfortunate part of the learning process while refusing to grant someone new to the hobby the same grace.
Frankly, I think some people also just like feeling the thrill of moral righteousness. Sure, they failed to recycle, cheated on their taxes, stole post it notes from work and lied about their phone being broken to avoid a call from mom--but they still get to claim the moral high ground.