His property, he can do what he wants.
That flag and what it stood for resulted in 618,000 soldier deaths and thousands more injured by hideous wounds and losses of limbs. Few today fully appreciate that the second worst thing that can happen is to have a war fought in your native land.
It takes two to tango. Someone had to fight the CSA. Whom was that and what flag was it? Obviously that one should come on down too.