citizens united: how it influences media

Billionaires David and Charles Koch have been handed the ability to buy our democracy in the form of giant checks to the House, Senate, and soon, possibly even the Presidency.
PBS canceled the airing of an expose of the Koch brother’s political operation when they – the Kochs- threatened to withdraw their support from PBS; and indeed they are significant supporters.
But why??
So they can be in a position to censor what’s aired on the county’s only non-commercial station.