My tips are between 18-30%, depending on the service. There are times when I didn't think the server was worth the 18%, but I put my money down anyway. Most of those folks depend on tips and, in many places, have to split their tips with the busmen, cooks, and bartender.
But I guess what chaps my cheeks more than anything else is the 2-pronged holier than thou approach of the patron. First of all, I don't give a damn that you give your God 10%. A lot of people do that and don't have to toot their horn about it. Secondly, why did he have to sign his name "Pastor"? Did he expect that to give him a pass on tipping? That term, at least in my mind, brings up an image of some Bible-thumping redneck that went to Bob Jones U or some equally repressed institution. The term "pastor" is normally used by a parishoner to describe his or her spritual leader. It's not a term you bestow on yourself. I gotta tell you, if this was my pastor and I saw that kind of rudeness, I'd be looking for another church before I left the table.