This seems to be the most common objection to inheritance taxes and yet it's one of the most inane.
Basically every transaction or net gain of money has been "taxed before". When you buy a copy of Bolt's trashy book, you pay 10% GST - but why? After all, that parcel of money you used has already been income taxed when it was passed over to you! And before that company tax was applied to your employer! It's not fair!