Well the OP got the answer. I have seen when Parents set the Content Advisor and children post to groups just like you did to undo it. Shame
My answer to this issue as I have learned over the years not knowing that if it is a bonafide request or not(most cases **not** when it comes to content advisor) is to tell the OP to call Microsoft.Let them take the blame.
Now I am not saying that this is the case with the OP here but........