The First Amendment is not and never has been outcome-dependent; the Government is barred from restricting speech -- especially political speech -- no matter the good results that would result from the restrictions. That's the price we pay for having the liberty of free speech. And even on a utilitarian level, the long-term dangers of allowing the Government to restrict political speech invariably outweigh whatever benefits accrue from such restrictions.
Read the whole thing.
(And yes, I realize that Greenwald would probably be the last person to characterize himself as being of "the left", but he is clearly no Republican apologist.)