Because infanticide - always immoral.
And if you are going to ask why, then honestly, when you use the word "immoral", I don't know what you are talking about.
Then you're going to have to define what you mean by that word to me first, because obviously, we have a different understanding of it.
No, I'm not going to explain to you why it is immoral to indiscriminatly slaughter a bunch of innocent toddlers.
Now you can answer my question:
Is there any action that your god could potentially engage in, that would be labeled as being "immoral"?
Note that I'm not asking if he would engage in such. I'm asking: is there an action, that if your god would do it, it would be immoral?
Because if there isn't, then calling your god "benevolent" or "moral", seems meaningless.