Slight nitpick, the lift of an airplanes wings does not negate the force of gravity. It provides a lifting force that is enough of an opposing force that it allows planes to fly.
If you look at thesaurus.com you'll see that "oppose" is a synonym of "negate." This is just semantics. Now, dictionary.com does give "negate" two definitions - one being to oppose (which was the intent of my statement) and the other being to annihilate, which is apparently what you took me to mean.
With that said, it's an interesting philosophical discussion (one that has occurred in professional literature) regarding whether forces continue to "exist" if their net sum is zero or whether that means they cease to exist.
Regardless, it's a semantic distraction from the discussion.
No, it would still be evolution. You have just applied a different selective pressure. Much like your flying analogy you have simply applied what was already there in a new way. Only now you are the moral agent making what most would call an unethical choice.
You seem to miss what I'm poking at. Does biological change include the human will? Is human morality part of what is "natural," or is the human will something separate that allows it to oppose nature?
If you include it, pretty soon everything is natural, and nothing is unnatural. As such, "natural" becomes a pretty useless word. Murder would be natural, and punishing murderers would be natural as well. I prefer to separate the two and think of the human will as something apart from nature.
It seems you would agree with me because you said:
I'll reiterate this because you seem to have missed it. Evolution does not posit how people should make decisions. It is not a set of ethical guidelines.
So, no, I didn't miss it. There just seems to be a bit of misunderstanding. Given the view as stated above, the human will can negate (i.e. oppose) nature. The question, then, is: should it?
Their is no such thing as a "darwinist". Their are simply people who find the large body of evidence of evolution to be convincing.
I'd refrain from making absolute statements if I were you. Note that I said "social darwinst." As such, you might want to study up on Herbert Spencer. Note that I also said maybe this discussion doesn't belong in the science forum.
Anyway, maybe the question is now clearer.