The function of spermaceti, i.e. the oil like substance in sperm whales, is unknown. But a lot of whale oil was extracted from heating whale blubber from different whale species.
You can absolutely render out an oil of sorts from human adipose tissue. This may happen after we die under certain circumstances and can be found as adipocere, aka corpse wax.
Hi, it's me, the devils advocate.
One could argue that every instrument made out of wood is needlessly taking lives, since the tree died. It's also possible to extend the argument so that every instrument is needlessly taking lives, since no matter what material you use requires use of energy and we have no way to generate energy without something dying.
The question naturally comes down to what is needless. Needless for what? Needless according to whom? When it comes to art, as music does, it is completely subjective. It is completely valid to think this use of materials is needless but who's to say what's correct. The marker of this probably didn't think their work was needless.