MSNBC, by refusing to let Senator Dennis Kucinich speak at their debate, is setting a very dangerous precedent. I'm not a Kucinich supporter, but like Ron Paul (who I also don't support), he is a dissenting voice in the elections. Virtually every candidate on both sides fits into a very narrow segment of the political spectrum. The fundamental political philosophies of Romney on the (relative) right and Clinton on the (relative) left are much more similar than either politician would care to admit. By censoring Kucinich, MSNBC is impoverishing the range of the debate (just like FOX has been doing with Paul). With so many problems facing the nation, perhaps some political diversity and fresh thinking is in order? Let's at least allow the edgier ideas to get out there.
But that's not the real problem - this situation demonstrates the mixing of corporatism and politics at its worst. A private company should not be able to dictate the political discourse of a democracy. The FCC exists because the medium of television has such a profound effect on the culture - the FCC is supposed to make sure "that operation of [television stations] would be in the public interest" (source). The FCC doesn't regulate cable, for better and for worse, so MSNBC is not under their jurisdiction. Nevertheless, the FCC's very existence highlights how powerful a voice television producers have, and how the government was cautious from the very beginning about limiting the power that the private owners of the medium have. Now that that power is so centralized, it's even more important to be cautious. And when networks like MSNBC presume to dictate the terms of American politics, they have more than overstepped their bounds.