Ask any gardener - plants do feel, remember, communicate. Whatever CNS or brain they have or haven't. Scientists just now have discovered what any breeder knows - chickens are intelligent. Not so long ago it was a universal truth that dogs can't think. And just a little more ago - that black people were ok to be enslaved because they don't feel pain (speaking about diamond mines with awful conditions). And all those views had a "solid scientific basis", just like Derp is arguing now.
Its nothing else than a mechanism of psychological self defense, a way to believe cruelty is ok, because that other one is inferior, at a level of an object. And schock when we discover that its not so.
P.S. still eating meat.