Try proving it, though. There's just about no evidence at all. Many Clergy were from Knightly families. Just look at the mythological Turpin from Roland or any Clerical combatant on a Crusade.

The only one indication it might be true goes back to Odo of Bayeux and his depiction in Wace's version of The Battle of Hastings, but I have yet to read it, so I cannot substantiate it.

The symbolic function of the Mace is another story, however.

Top it off with the fact that Clerics were modelled on Templars and we are completely lacking a 'historical' reason to restrict them to Maces.