Why would God have need to keep children alive if he can read their hearts and know what they will turn out to be?
In Isaiah 46:10 God says....
"From the beginning I foretell the outcome,
And from long ago the things that have not yet been done."
There can be no injustice with one who is all knowing. This is why we trust our God implicitly. He does not make mistakes....and he tells us what his intentions are, and why he does what he does, the way that he does it. The long term benefit is always at the fore. The end always justifies the means.
Let me ask you....if you come upon a nest of very venomous spiders in your home, would you kill just the parents and spare the babies because they can't kill you yet?
Will those babies grow up to be just like their parents? I don't know if you've noticed, but today's children seem to have very little empathy unless it is instilled by loving and empathetic parents. Sad to say too many children are raised by parents who mirror their own poor role modeling. It can be perpetuated over many generations. Drug addicted children are often the progeny of drug addicted parents. Alcoholic children repeat the habits of their alcoholic parents. Kids who see violence at home will often carry it over into the school yard and feed it with violent video games.
When this world goes down, as we believe it will in the not too distant future, only those who have bothered to search for the true God on his terms, and who are willing to change their ways, will find him. Those who want God to fit their terms will be very disappointed.