You can still think it's wrong even if you don't know how to intervene to improve the situation. Non-interventionism isn't the same as acceptance.
Just like if you see someone getting beat up on the street and you don't try to help just means you didn't know how to help, not that you thought it was right.
Oh eating babies and sacrificing I think is wrong for sure.
If it's a self sacrifice for whatever they believe, I don't think it's for us to interfere. I don't have an answer for more extreme things though, like baby eating, forceful sacrifice and such. If we can educated or somehow change their minds I think it's good, but if it becomes oppression from our part, imprisonment, more deaths and etc, I think we should not involve.