How is a mixer "unethical"?
Is it unethical to have window blinds so anyone that wants to can't look into your house too?
Is it unethical to use cash since it doesn't have a tracking microchip in it to see where you're going with it?
I mean, should the exchange tell it's customers whether or not it mixes their coins, and then if it mixes them with non depositors coins as well?