"The vast majority of anti-whaling advocates believe that all species
are on
the verge
of extinction"

Your reference for saying this? Link, please. I never heard anyone
say that.

"True animal
intelligence is measured
by behavior and social interaction..."

Adjudicated by humans. Some creatures, like porpoises, apparently use
their large brains to have fun all the time, and some creatures, like
humans, use their large brains to kill everything in sight, including
each other.