Heroic pity

Nietzsche again. I'm sure I'm very far from being the first reader of Nietzsche to be struck by the strange weighting of his anti-pity position. From Der Antichrist [7]:

Pity stands in the antithesis of the tonic emotions which enhance the feeling of life: it has a depressive effect ... pity on the whole thwarts the law of evolution, which is the law of selection. It preserves what is ripe for destruction; it defends life's disinherited and condemned; through the abundance of the ill-constituted of all kinds which it retains in life it gives life a gloomy and questionable aspect.

The thing to do here is not to deny Nietzsche's premises, or to dissent from his anti-Christian perpsective; but rather to wonder how this position squares with the philosophy of heroism he is advancing. Pity here is deplored because it contradicts 'the law of evolution'. There is a misunderstanding of the way evolution works here, I think, but never mind that for a moment. Instead wonder: in what way is it the action of the noble, the elite, the best ("...in every noble morality it counts as a weakness...") thuswise timidly to accede in this evolutionary law? Is it not nobler to defy nature, whether or not such defiance is materially productive or not? To say, in heroic tones, "nature demands this hecatomb of the weak; but I chooose not to supply it"?

It may be possible to work out what I'm reading on holiday, right now.