The point, however, is that death is clearly extremely harmful. That's in the bank. There's no serious dispute over it. — Bartricks

What about the sacrifice of one life to save millions of other lives? That seems like a death that is extremely helpful to millions (assuming they are not suicidal).

(What if Hitler could have been snuggled to death as a baby?)

Yes, that just serves to underline the point. Killing yourself to save others from a similar fate is - sometimes - rational because it is sometimes the right thing to do. But it's the right thing to do 'because' death is so harmful, not because it's nothing or no more significant than a stubbed toe.

I was also careful to say that escaping extreme agony is what it seems to take to make suicide in one's own interest. That is, it's what it takes for one to have 'instrumental' reason to kill oneself. Instrumental reasons are not moral reasons. And sometimes we might find ourselves with moral reason to kill ourselves if, say, doing so will save the lives of countless others or some such. (There are other ways too - one might come to deserve to die through one's atrocious behaviour, for instance).

The point remains that all of this is evidence of just how harmful death is to the one who dies. And thus that's probably why religions condemn it as immoral. It isn't actually immoral, at least not in the main (it's irrational in the main, but not immoral). But it is so harmful to the one who dies that it makes sense to condemn it morally, so as to reduce the chances of someone subjecting themselves to it. For someone who is in, say, the grips of depression or some other mental episode is typically not going to be very good at thinking about what is truly in their own best interests, but they may still be motivated to do what is right.

(What if Hitler could have been snuggled to death as a baby?) — Merkwurdichliebe

Nazism would be able to exist anyway. Hitler was not the only chain of Nazi Germany. The führer could be elected on Goebbles or Himmler, for example. There are some facts inside history that looks like unavoidable.
WWIII and Nazism had to exist to take a good lesson from it. I mean, soon or later, this kind of world issues happen.

What if Putin could have been snuggled to death as a baby? ... well I guess another Russian oligarch with another name would have attacked Ukraine too.

Fun facts

1. Animals don't suicide no matter how extreme their suffering.

2. Humans suicide when extreme their suffering.