Answer

I don’t know who Rabbi Mali is, but “do not let any soul live” was said about the seven nations or Amalek, and that’s it. If he has interpretive innovations, very nice, but to go out and commit genocide on their basis is excessive—especially since this borders on deriving law from the reason for the verse, and with some strain one could perhaps say that this is the definition. About that it was said: just because we imagine a similarity, should we act on it?! Beyond that, there is also the law of the nations (international law) and morality, to which we are bound.
Pay attention: I am not talking about a situation in which one must harm uninvolved people in order to save oneself or rescue hostages. It is obvious that this is permitted and required, with no connection whatsoever to “do not let any soul live.” For that, there is no need for newly invented interpretive moves. Perhaps that is what he means, and he behaves like all those who enjoy finding everything in verses (through no fault of the verses) even when it is just a simple logical argument. But the claim that they should be killed even when this is not needed for our rescue is a very major interpretive innovation, and deriving law from the reason for the verse. To kill on the basis of such a thing is criminal recklessness.