This isn't how DFT was explained to me. The differentiating points are: 1. Aliens would kill us because they cannot determine if we are an existential threat.

This isn't how DFT was explained to me. The differentiating points are: 1. Aliens would kill us because they cannot determine if we are an existential threat. If they assume we are friendly and we are not, they are dead. It isn't about resources, it is about destroying your enemies before they evolve the capability to hurt you. There is no good way to monitor or communicate with a civilization more than a couple dozen light years away, physics doesn't allow for it. By the time your message gets there the entire government, culture, etc of the planet has probably changed. 2. They would use long range missiles (e.g. an asteroid going sufficiently fast) to wipe out the planet, not an invasion fleet. This means that they don't have to have the capability to travel in deep space, just to throw big rocks. 3. This is all predicated on a few assumptions: that no aliens are living close(r than 400LY) to us, developing the capability to fling rocks at a star or planet isn't extremely difficult, and that once the big rock is in motion, there is no good way to defend yourself against it (except sniping it with another big rock, but that's probably magnitudes harder than hitting a planet). I don't know enough about biology to dispute the thing about biomarkers, but that would put a huge dent in DFT. And I agree using it to make policy decisions is dumb.