I don't think he is afraid of her. He may not want her parents to be guardians and have access to medical and financial records. No telling what is in there. Remember the xrays that were hidden from them,the ones with the proof of spousal abuse.
Which is why he wants her body creamated as well, also against her religion.
These days, the Catholic Church does seem to accept cremation .. however, that's not the issue with GRRReeer's inappropriate ruling on the subject.
I am Catholic, and it is not against the religion for cremation...you just have to inter the ashes, not keep them in your living room or spread them over Niagara falls.