PETA always said that animals should be treated like humans. Unfortunately for the animals under PETA’s "care", that apparently means imposing the same quality of life ethic advocated by the likes of Henry Morgentaler: better to be dead than to live under less than ideal conditions.
Since "ideal" is a purely arbitrary standard and PETA seems to define it for animals as "Able to own your own three bedroom home free from human interference", it believes it is better for a animal to be dead than live as a pet. As such, PETA kills thousands of animals a year, sometimes in ways that get them arrested.
UPDATE: Debra Saunders offers some background information for this story in this very interesting piece.