So, I read the article and (most of) the study, and the thing that stood out to me was the researchers' conception of judgmental attitude and altruism.
From the article:
The study also found that “religiosity affects children’s punitive tendencies”. Children from religious households “frequently appear to be more judgmental of others’ actions”, it said.
Muslim children judged “interpersonal harm as more mean” than children from Christian families, with non-religious children the least judgmental. Muslim children demanded harsher punishment than those from Christian or non-religious homes.
It makes sense to me that people from religious homes would see behavior that causes "interpersonal harm" as unkind. It makes sense to judge it that way. They are thinking consistently along the lines of their particular worldview. For example, a Christian child sees one child push another without reason or cause, which would be a violation of the law of love ("Do unto others as you would have them do unto you"). It makes sense that they would see it as a violation and not shrug it off as no big deal.
Moreover, it makes sense that they would want to see some sort of justice done to the one who offended another kid. While they aren't showing empathy toward the kid doing the pushing, it would seem that they are being empathetic toward the child who has been treated poorly.
So, are we saying that it's a bad thing that religious children get upset when they see injustice and call it injustice? How is that not empathetic?
It seems to me that altruism is being defined as sharing your stickers and looking the other way when others are being pushed and shoved.