What we learn from animals doesn't make it justified, but it might explain our own quirks. For instance, homosexuality is well-documented in animals, which is a neat counter to the position that sex is only "naturally intended" for procreation. And studying animal behavior may expose evolutionary reasons for said behaviors, which helps us understand and sympathize both with animals and with our fellow human beings. For the latter, it may lead to more effective treatment. For the former, it's just really funny. Because who doesn't want to see a drunk elephant or a stoned water buffalo?