The question is why anyone who isn't far-right would view ancient Sparta with anything but horror and contempt.
Well, historically it was viewed very positively by the radical left as well, going back to Rousseau. Very much the preferred Polis of the Soviet Union. But, again, that is not so surprising!
Oh, of f**king course. Everything awful about the left since 1789 can be traced back to Rousseau, it seems.
Like...popular sovereignty? The idea that inequality is an unnatural social imposition? I think it's somewhat fair to call Rousseau a paranoid semi-lunatic, but the Bertrand Russell thesis of him as some irrational totalitarian who poisoned western thought is a ridiculous exaggeration.
Among other reasons Rousseau liked Sparta for its egalitarianism and communitarianism, and his distrust of the bourgeoisie and their values. With some (ok perhaps major in places) qualifications, fair enough really from a leftist perspective.