Restaurant Tip as Christian Witness?

Okay, so this apparently has been around the news for a while, but I missed it.  It's about this pastor in St. Louis who was at an Applebee's in a party of 10.  When she got her bill, she noticed that, as per restaurant policy for large groups, an automatic tip of 18% was added to her bill.  And what did this pastor write on her bill?  "I give God 10%.  Why do you get 18%?"  And then she signs it "Pastor (Name)."

Really?  That's how we give witness to the world as pastors?  I'm ashamed and embarrassed.  I can't speak for the Almighty, but I can imagine Jesus might be a bit embarrassed as well.