since they're the ones who really glorified Sparta first
As I tried to point
above, the first to have glorified Sparta were Athenian aristocrats, for their own political needs against democratic factions.
(it's also why the Roman war god Mars is a much nicer guy than Ares)
Probably as well because they were two different divinities. Mars appears to be originally a defender of farmland in the Roman archaic religion, then extrapolated to war, and just war with that (which makes him closer, if anything, to Athena than Ares).
The
interpretatio is essentially a later mechanism without real grasp on spirituality : the same way Venus is FAR closer to Astarte than Aphrodites, for exemple.
Secondly, modern excavations in the chasm that was meant to have been where the Spartans threw their children have only turned up adult skeletons, according to the swiss excavation team - so whilst there is a legend, Dogson may well be right. At the very least it is disputed, and believed that these skeletons may have belonged to criminals.
We shouldn't forget that Sparta's traditions, or rather what we know of it, are largely parasited by Late Sparta (critically in Roman times) own...proto-tourism is how I'd put there. There were public displays of such traditions, more or less degenerated or revived attempts at tradition, for the benefit of visitors.
That said, infanticide isn't unheard of : it's remarkable that no author at my knowledge denies that in Ancient times. At the leatest, it have been a really widespread tale, geographically and temporally.
And as you mentioned this article, I should point you that such infanticide isn't unheard of in Greece outside Sparta, but as well in other regions : Carthago comes in mind, even if there may be confusion with particular rites of burial who may have existed instead OR in parallel, or in Rome (critically with the pater familias authority on his child (including newborns).
"I am still in Alexandria. ... I beg and plead with you to take care of our little child, and as soon as we receive wages, I will send them to you. In the meantime, if (good fortune to you!) you give birth, if it is a boy, let it live; if it is a girl, expose it."
There's quite a trend nowadays about white-washing ancient civilisation from what we consider, and rightfully so, as abominable. But it existed (while not exactly normative), and was part of this ancient culture : denying it wholly (when it's, shall we say politely, a really debated question) have often some not-quite honest reasons.