I have heard this argument before, but if I don't understand animal sacrifice either.
How can killing a sheep please God ?
The act of offering something to a deity is an act of gift-giving that invites reciprocity. Religion in the ancient world was primarily
transactional, in that the internal logic of ritual was to forge a relationship of mutual reciprocity between the divine and the human.
To describe animal sacrifice, as some have done here, as the act of giving up a valuable livestock animal is missing the point. In nearly all ordinary cases of animal sacrifice, the animal was cooked and eaten by the human celebrants (typically either boiling in a stew, or roasted at the altar fire). The sacrificial act is the act of building and maintaining relationship with the divine by offering the animal's life to the gods, and the subsequent consumption of it by the celebrants is the follow-through of the gods providing the flesh of the animal to humans as a gift in return. In certain situations, typically dire though it also arose when dealing with the spirits of the dead or underworld gods, an offering would be burnt entirely; but this did not constitute the majority of animal sacrifices.
It "pleases" the gods in the fact that you are giving something to them, showing that you respect them as Powers and inviting them into your home, your life, your community. Maintaining a good relationship with the gods through this repeated, mutual reciprocity was the entire goal of ancient city-state religions. Judaism was no exception to this complex of ideas and practices. It was ubiquitous across the ancient world. Whether you agree with this mindset or not is
completely irrelevant. It is understanding the internal logic of it that is vital to understanding how Christianity derives the concept of Jesus-as-sacrifice.
I'd recommend reading Walter Burkert's
Homo Necans, which goes into detail about the theory that sacrificial ritual derives from neolithic hunting rituals. His book
Greek Religion, while obviously focused on the multifaceted religious life of Classical and Hellenistic Greece, also contains a lengthy delve into ancient sacrificial ritual, its socializing function, and the internal logic related to hospitality and reciprocity. If you care about understanding the ancient ritual mindset, and aren't just Bitching About Shows You Don't Watch (but applied to religion), I'd recommend reading them.
