I think it entirely depends on the strictness of the religion, what the religion is, and the manner in which it is being instructed.
For instance, I believe that telling any small child that there is even the concept of a Hell is abusive. Telling a child that they are anything less that fine and perfect the way they are is abusive. Telling them they are not "good enough" in any way is abusive. Some religions restrict what you can do, say, think, believe, in such a way that it is psychologically and emotionally traumatizing for the children.
I don't find anything wrong with a child believing in fairies or angels or praying to a god or goddess for a new teddy bear or whatnot. Children, if let to think and reason for themselves as they age, will naturally decide what makes sense for them to believe. Indoctrinating them into a strict religion that monitors and decides their every step...hinders that natural progression...and that is what is abusive.