Some food for thought: John Stuart Mill said it best, in On Liberty (1859). Everyone, Mill noted, claims to believe in freedom of expression, but everyone draws his or her own boundaries at the obviously worthless, dangerous, and wrong. Why should we tolerate speech that offends our sense of essential value, security, and truth? Mill answered four compelling grounds for doing so: 1) the opinion might be true and "to deny this is to assume our own infallibility"; 2) the opinion, though erroneous, might, indeed, most probably would "contain a portion of truth," and because "prevailing opinion" is rarely, if ever, "the whole truth," censorship denies us that possible "remainder of the truth" that only might be gained by "the collision of adverse opinions"; 3) even if prevailing opinion were the whole truth, if it were not permitted to be contested--indeed, if it were not, in actual fact, "vigorously and earnestly contested," it will be believed by most not because of "its rational grounds," but only "in the manner of prejudice"; and 4) if we were not obliged to defend our belief, it would stand "in danger of being lost, or enfeebled, and deprived on its vital effect on the character and conduct," becoming a formula repeated by rote, "inefficacious for good . . . and preventing the growth of any real and heartfelt conviction, for reason or personal experience."
from The Foundation for Indivual Rights in Education