Yes, but talking about Christianism, you are forgetting one thing.
You should share and aid people with anything, but you should never negotiate your salvation or your connection to god.
So yes, by saving the baby or even killing christens you would be making them a favor BUT you are screwing yourself yourself in the process because god should be over your friends family or offspring.

Didn't Andrea Yates have something akin to this line of thinking when she drowned her 5 kids? In her severe mental instability, she came to believe her children were influenced by Satan and she couldn't save them except to kill them.

I'm more inclined to agree with Mofo1953 on tnis issue.

You could even call it a gift.

Andrea Yates drowned her five kids in the bathtub, apparently believing they would all go to heaven. (Apparently she was told by medical professionals not to have any more children as her post-partum depression/psychosis would return. They apparently ignored this, having more children, stopping her meds, and finally drowning her children.)

that was the same logic the catholic church used to slaughter millions all over the world, weirdly enough

I've had the same thought

This logic you are using is antinatalist in nature. I am not accusing you of being antinatalist, but the logic of your question embodies antinatalism.

Proponents of this philosophy believe that is morally wrong to procreate. The reasoning relies on the belief that the inherent suffering of life(Hell) far outweighs the positive aspect of life (Heaven) so much that it is ethically wrong to want to continue propagating life.

They take Heaven and Hell, put them on earth and ask, "Don't you think it is better to spare these kids from existence knowing what you know?

A questionable debate stratagem.
Also:
[en.wikipedia.org]

Yes, it would. The flaw there it doesn’t allow for the Catholic Church to outnumber all the others on the planet. Stealth by numbers.

Das fuct up right der

Logic: Not Religion!