I don't believe the Romans were that accomodating to the requests of prisoners as to respond positively to their requests.
It was more probably that Nero decided to take cruelty up a notch with someone who irked him hard.
The whole upside down cross / black mass thing was actually started by monks/priests in rebellion who had been pressed into service by low born parents who wanted a better life for them. In that time period you were either born Noble or went into the priesthood, the only ways to have an education and shot at a decent life. The rest were basically serfs and peasants. Thus they resented their forced lifestyle and rebelled, creating what transformed into "satanism".