I am not a fan of Peta. However, PETA is a red herring in so far as this particular subject goes. Its like arguing that since radical environment groups are against pollution, it should be ok to dump oil in a creek because those groups are nuts. Even if PETA never existed, it would not change the fact that unlike the vast majority of animals, Dolphins, Orangutans, Elephants, Chimps, and Bonobos, are self aware. Your dog is not truely self aware, neither is your cat. However, those animals, just like the human animal, are. Moreover, all those animals pass learned knowledge to their peers and offspring. All of those animals have primitive cultures that change over time. All of those animals morn their dead. All of those animals are capable of empathy and have primitive notions of right and wrong in terms of injuring others.
I don't know if they should be granted person-hood or not as that is purely a human construct anyway. However, its immoral to treat any animals that have those traits as "property".