You anger is refreshing, but did you consider that the nomination is not an election, and thus indeed belongs to the Democratic Party, not to voters? Voters have their say later. Colbert is free to register as an independent.
Eliezer, what's this with your recent bias against boredom?
Are you sure it's rational or efficient or even simply useful in any way to cultivate a constant (and possibly boring) battle against boredom?