Why would animals get benefits from "loving your enemies"?
I just stumbled on this article which says:
"This paper presents and criticizes. Alexander's evolutionary theory of morality (1987). Earlier research, on which Alexander's theory is based, is also reviewed.
The propensity to create moral systems evolved because it allowed ancestral humans to limit conflict within cooperating groups and thus form larger groups, which were advantageous because of intense between-group competition. Alexander sees moral codes as contractual, and the primary criticism of his theory is that moral codes are not completely contractual but also coercive. Ways of evaluating Alexander's theory as well as modified versions of it are discussed."
The red part seems to line up very much with what the poster Cypress said about "morality" can have an advantage for the animal. And this seems to posit a means by which larger groups can be GROWN by cooperation (peace as opposed to war). Might be over-interpretting this, though. And it doesn't address the question of why would an animal help a fellow sick animal (even though we know they do, but that's probably because they don't necessarily know that some sickness can spread).
The article is here:
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-9744.1991.tb00803.x
You can even get the pdf free I think.