Justin's father had already paid tax on what Justin inherited. (income tax, capital gains, etc.)
If there were estate taxes, or death duties, the howls of protest from every beneficiary (not just "the rich") would drown out any other political storm. 
Beneficiaries don't even like paying probate fees, and they deeply resent the estate having to pay the income taxes that come due on RRSPs and other tax sheltering mechanisms at death.