There is a huge difference between a deranged maniac *thinking* others are to be exterminated for whatever reason, and people actually *being* so rotten that they need to be exterminated.

Sure there is. That's why it's not a good analogy.

There are two reasons why I think the comparison was probably made. One is that both cases involve genocide. The other - and this is the arguable one - is that they were both unjust.

Your argument regarding the children is fine as far as it goes, but still does not apply to very young infants - unless you think that children are irreversibly corrupted right from birth.