Fairly simple, they want conformity. The freeper who posted the quotes from Farenheit 451 hit the crux of the issue. The goal is to banish independent thought for the ultimate control of society. The communists did it various ways. The flag banners won't need to ban certain books because half the sheeple will self-censor. Not only that, they will ostracize those who do not self-censor. It already happens. Try being politically incorrect in a corporation some time.
The current method of enforcing conformity is demonization (e.g. of the Confederate flag). Having succeeded they can demonize anything else they want by associating it with the slaughter of innocents as was the case in Charleston. Christians are not far down on their target list even though Christians were slaughtered. Don't be surprised if the next "right wing" wacko is ID'd as fundamentalist.