Two objections:
1. Serwë is damned according to Kellhus
2. Kellhus sees a babe getting feasted on by Ciphrang in hell
How many mothers and babes has the Judging Eye looked at though? Not too great a sample size.
Isn't calling 2 datapoints an insufficient sample size problematic when you use 1 datapoint to support each of your arguments? lol, lets not get all pedantic, and we both know the sheer volume of datapoints doesn't make for a good argument either, so its just a bad measure all around.
I get what you're saying - yes if we were doing a scientific study a sample size of 2, or 1, wouldn't be enough. But we aren't. Its a book, and we've been given the evidence that we have available.
Unlike the Outside though (and the accounts therein), which we have constantly conflicting evidence from all sources, TJE provides absolute truths - its a pretty fundamental part of the world building.
The nature of that truth isn't particularly clear, but I think in this case its strongly suggesting that Mothers and Babies are holy for whatever reason, and there's little that conflicts with that.
Isn't it a bit problematic that you can justify anything with "well, Kellhus/Bakker are unreliable so textual evidence doesn't count" though?
Any argument, regardless of it's veracity, can be taken out of context and be made to sound silly. (("Global Warming? Ha. Look there's ice right there"-
XKCD for the lulz. Not a commentary on global warming btw, but the improper use of logic without proper context.))
Could it be problematic to make that a blanket statement to justify or remove any argument? Yes, obviously. That's why we attempt to corroborate with other evidence when we can.
The specific problem with Kellhus is that we know he lies, a lot, more so than any other character. We also know that he was going insane, and being partially or fully controlled by Ajokli. So an insane liar being controlled by others entities doesn't make the best witness ever, which is why using Kellhus creates a difficult position.
I'm not outright dismissing him, but context for him is super important, and because so much of what he says and does is interpreted differently by different people, just using Kellhus makes for a fairly weak position.
As I said, his observations in the Outside, or wherever it was he was, does provide some counterpoint to the theory being discussed. But again, a weak on imo. How old were the babies? Kellhus refers to Men as Children, perhaps his POV 'babies' are anyone less than 15 years old? 10? 5? How old does the initial holyiness of creation last? Earwa damnation isn't particularly fair, could be as soon as the little buggers start crying and pooping on everything the gods send them straight to hell.
Maybe it points to something else though as well, if in fact babies of any age are in the place Kellhus was. Perhaps not that the child is holy/saved, but maybe again pointing to the mother - the womb, the place of creation, being absolutely holy.