The absolute scale for other species is more like "is a pet" vs "is not a pet". Humans kill other humans without too much hesitation if they can convince themselves that those other humans are sufficiently different from their in-group.

Parochial altruism is an adaptation to resource scarcity and danger. An advanced civilization will be less affected by such problems.

I think it's quite risky to assume anything about alien psychology.

Agnosticism is useless for the purpose of decision making, it only suggests that all decisions are equally good.

I suggest acting according to worst case assumptions, not weighing probabilities equally.

Worst case is when you choose a wrong strategy.