You can kill a fly and nobody cares but not a seal.

           I guess size and cuteness are major factors.

Size because look at the blue whale vrs. bakteria . Cuteness because look at baby seals compared to sharks. So how can we blur these lines, well.

                  What if you had a huge wall projector that displayed a black widow about 30 long and then you stuck pins in him all the time and you could have a microphone hooked up to hear her screaming. Or if you made baby chicks wear little Dave mathews t shirts. In that case I would feel bad for the spider and probably had a very short kick boxing match with the chicks.

      Shmed.