But there are also people who just oppose utilitarianism, like G.E.M. Anscombe. For instance, in https://integrityproject.org/wp-content/uploads/2015/07/mr_t..., she seems to grant that dropping the nuclear bombs on Japan was probably good from a utilitarian perspective (because it saved lives overall) and also to grant that bombing campaigns that necessarily entail massive civilian deaths (including, apparently, area bombing German cities) are morally permissible but still to argue that dropping the nuclear bombs was impermissible because it constituted murder ("intentionally" killing the innocent). But this kind of distinction, which I think is what actual anti-utilitarianism must come to, is hard to even consistently maintain, and I suppose many HN readers would find the effort quixotic.
It is relatively easy to take the proceeds of a massive fraud, buy a relatively small (as a percentage of the fraud) $ amount of mosquito nets, and save more lives than the lives impacted by your massive theft. Is this a correct application of the utilitarian calculus? What sort of data would we need a priori to do this calculation "correctly"? Do you think he had a careful estimate of the suicide rate of victims of ponzi schemes before perpetuating the fraud, or would any suicide rate have made the decision net [pun intended] moral, as any such victim of fraud would lead to >> 1 net purchased (so you would almost always net save lives).
The above is of course snarky. It is also a best-effort way of analyzing a notable utilitarian's actions. I do not think it would be difficult at all to use this type of argument to argue that SBF's actions net raised utility in the world. If only we all would become fraudsters, then we could truly live in Omelas --- a notable utilitarian paradise.