But is the death penalty really a reasonable response?
It is just a bowl of tragedy down in the trenches.
Mass killing of animals is not genocide in any form. Your philosophy might deem them equivalent and I respect that view, but you should accept it's an extreme, minority position.
The major problem with genocide is not the disparition of a culture or ethic type, it's the killing of scores of humans that have value unto themselves.
In contrast, the vast majority of legal systems and societies in existence today do not recognize the mere killing of an animal as wrong. Humans widely believe they have the right to take the life of an animal, as long as it'd done humanely, for sensible reasons and does not threaten biodiversity.
So genocide and extinction are fundamentally different, orthogonal moral issues.
Genocide is a relatively new term, created to describe the Nazis. It combines the word genos, which means race or tribe, and -cide, death.