The CPA firm I first worked in was founded by an old ex-IRS agent.  He had retired by the time I started but I heard plenty of "Elmer" stories over the years.  He once had someone question his secretary about the preparation fee.  He overheard the conversation, walked up to the client, and asked to see the return.  He grabbed a good hold of the return, ripped it in half, tossed it in the garbage can and told the client not to let the door hit him in the a$$ on the way out.  When I first started my practice, my response to your client would have been the same as yours PA.  But after a lot of years with dealing with all sorts of personalities, my current treatment would be the "Elmer" treatment.