There are no rules requiring minds to value life, liberty or the pursuit of happiness. An alien will have, in all probability, alien values. If an "alien" isn't evolved, the range of possible values increases even more, allowing such absurdities as a Paperclip maximizer. Creatures with alien values might as well value only non-sentient life, or they might spend all their time building heaps of prime numbers of rocks.
Related tags: Complexity of Value, Orthogonality Thesis, Mind design space, Paperclip Maximizer, Ethics & Morality.