.
I have two:
1) I've stolen this from the great President Trump. Whenever someone wants me to do something and I don't want to, I just say, "I can't do that. The Kurds didn't help us at Normandy."
2) This is from the 1980s movie "Cobra" and is excellent for dealing with recalcitrant customers in business situations.
Customer: I want X.
Me: I can't do that.
Customer: Why?
Me: I don't deal with psychos...
