If one of the purposes of life is to learn love and compassion, why does Nature set such a bad example by allowing predators?

This has already been answered in part. We must remember that love and compassion can be learned only in a setting where there is call for their expression. Nature, being an expression of the Supreme Spirit, does not set anyone a bad example. Left to her own devices she will always achieve the right balance and harmony and if human beings lived in accord with Nature then our world would be a paradise. There are predators, but that is part of the way Nature ensures the survival of the fittest. Yet it is only one aspect of natural law at work. The essence of Nature is cooperation, for Nature is symbiotic. For example, a gardener who prepares his garden and co-operates with Nature obtains beautiful results. Probably the greatest predator on Earth now, the most destructive creature that has been known for many millennia, is man himself.