What would be the harm?

[Angrboda]

Oh, gotcha.  I thought you were suggesting burning out our neighbors was a moral proposition.  Now that I understand, allow me to object to what you meant.  As an individual act, burning out my neighbors has advantages.  However if I further a world in which people are allowed to burn each other out ad libitum, then that threatens the security and safety of me and mine.  I have a definite biological interest in the safety of me and mine, so I have a biological motive for forbidding such things, and refraining from them for fear that might prompt others to do likewise to me, regardless of how advantageous it might be for me to act thus otherwise.  So, no, this is not an example where morals are in contradiction to evolved needs and biology.  The problem is the lack of universalizability of the act.  An act which is in accord with my interests can quickly become contrary to my interests if universalizing said behavior would impinge upon the survivability of me and my genes.  This is why most moral frameworks, such as Kant's, have universalizability as a key feature.

None of that matters to evolution.  Aggressive and lethal competition for resources benefits the individual who prevails and weeds out those lesser genetics from the pool.

You may have a definite interest, but to call it a definite biological interest is to subtly conflate that with the interests of evolutionary biology, which don;t give a shit about you and your interests.  Additionally, while you posit that you have such a rational self interest..if you really were the biggest and the baddest in the land your rational self interest would rationally lead you to burn out the weaklings.

In all of this, remember, that by mooring your moral propositions (not your apparatus, your moral propositions themselves) to the whims of evolutionary biology or survival you are explicitly tanking the meaningful objectivity of a moral system in ethical terms.  You are setting it up to be knocked down, and with ease-

-naturalistic fallacy.

If that which is good is, more properly, that which is good for survival, it is an instrumental good, and not an intrinsic good.  It is not a matter of the fact x, but some other fact, y, to which x is applied as leverage.  The good, rather than the good for, could very well be (and often is) z.  It may be natural to do x, because of y, but that won't change the fact that it is z, and not x or y which is good (obviously, supposing that there is such a fact)...and that the fact z is that x is bad.

All that matter is whether there is a selective pressure against it or not. People who belong to societies where such things are accepted do not prosper as well as societies where such behavior is not tolerated. If the society suffers, so do the individuals. If the society benefits, so do its individuals. As they say, a rising tide floats all boats. It has nothing to do with reasoning toward it being in one's interest. So, no, you're simply wrong about it not being a biologically based impulse. It most definitely is.

I don't know what your point about mooring morality to its evolutionary roots is, you're not particularly clear here. Moreover, for someone who takes harm as the objective basis of morality, I find this a rather strange position to take, as it seems to undermine your contention that harm is an objective moral standard. The moral standard of harm is quite obviously tied to biological interests. Have I misunderstood you?