I always interpreted "our kind" as the whole of humanity,

Did you read the linked article? In it Eliezer is contrasting rationalist and religious institutions. You may also want to read this to get an idea for the problem James Miller is trying to address. Here is a relevant quote:

Suppose that a country of rationalists is attacked by a country of Evil Barbarians who know nothing of probability theory or decision theory.

Now there's a certain viewpoint on "rationality" or "rationalism" which would say something like this:

"Obviously, the rationalists will lose. The Barbarians believe in an afterlife where they'll be rewarded for courage; so they'll throw themselves into battle without hesitation or remorse. Thanks to their affective death spirals around their Cause and Great Leader Bob, their warriors will obey orders, and their citizens at home will produce enthusiastically and at full capacity for the war; anyone caught skimming or holding back will be burned at the stake in accordance with Barbarian tradition. They'll believe in each other's goodness and hate the enemy more strongly than any sane person would, binding themselves into a tight group. Meanwhile, the rationalists will realize that there's no conceivable reward to be had from dying in battle; they'll wish that others would fight, but not want to fight themselves. Even if they can find soldiers, their civilians won't be as cooperative: So long as any one sausage almost certainly doesn't lead to the collapse of the war effort, they'll want to keep that sausage for themselves, and so not contribute as much as they could. No matter how refined, elegant, civilized, productive, and nonviolent their culture was to start with, they won't be able to resist the Barbarian invasion; sane discussion is no match for a frothing lunatic armed with a gun. In the end, the Barbarians will win because they want to fight, they want to hurt the rationalists, they want to conquer and their whole society is united around conquest; they care about that more than any sane person would."

And that's assuming the rationalists don't simply surrender without a fight on the grounds that "war is a zero sum game".