We don't ban, we never ban OBVIOUSLY!
Because 3 words: Freedom of Speech, or freedom of artistic expression, freedom of opinion etc.
Banning, censoring, forbidding are all signs of an ignorant society that can't stand dissident points of view. Banning/censoring is the root to dictatorship. It's the implicit admission of one's limitations and it's a way to prevent progress. A lot of progress has come to be because some people bravely stood out against the ideas and mores of their times. (And the stupidity of their peers)
NEVER ban the last temptation of Christ or The realm of the senses or the written works of the Marquis De Sade etc...
Banning/censoring someone else's opinions/ideas/artistic works is for weak minds and as history has it, too many weak minds hold way too much power in this world.
(Don't I know something about it )