(*) Let us note that when he said "if a man strikes you on one cheek, offer him the other", he didn't add, "and go on doing it as long as he wishes". What is being spoken of here, is patience, not submissiveness. That is, one is to give those doing one harm, a chance to come to their senses, instead of seizing on the harm as an opportunity to immediately "get them". Leave the door open to repentance, and forgiveness on one's part.
(1)"Prejudice", here, will be defined as a diminishment of the desire to accept another into one's community, leading to an unfriendly response should he attempt to join it, which is motivated by traits the other possesses, which in no way negatively reflect on his character.
It is, in the context of this article, to be distinguished from bigotry, which here we will consider to be a malevolence toward the other, based on those traits. The difference, is akin to that between not enjoying another's company, and hoping that he will suffer, no matter where he goes.
Given how many of those online, have been so greatly unpopular off-line, it is small wonder that blurring this distinction has become so popular on so much of the Net. Very often, the transferrence of the justly popular scorn that attaches to the act of openly wishing another ill (without justification), to the lack of a desire to socialise with someone would prove most convenient for a writer, who would be seeing far more social (and perhaps romantic) invitations, if others felt guilty for declining to offer them.
(2) Above a certain level, of course, a tribe or people will be driving out so many productive members, as to fatally weaken itself.
Eg. Nazi Germany, emigrants from whose power bloc ended up creating much of the weapons technology that was to give the US supremacy.
(3) To borrow a line from Robert Frost, "Good fences good neighbors". (See "Mending Wall", a pleasant little poem that's been known to drive the politically correct absolutely insane).
(4) The case of the attempted forced westernization of Iran under the last Shah during the 1970s is an infamous case of this. Relatively permissive western values were imposed on a deeply Islamic population, and then an attempt was made to squelch dissent. The end result was proverbial. Society, there, became more fanatically, and more violently, intolerant than it ever had been, before. The freedom of woman to go unveiled, briefly, was bought at the cost of woman having acid thrown in their faces for doing so, later.
Moral of the story : suppressed speech is not just simply forgotten, and you can't force people to be what they're not, without a backlash following, regardless of whether it is what they "should" be, or not. The only thing one succeeds in doing, is stifling the discussion that would have allowed people to find a more moderate response they could live with, and that would have persuaded them to adopt it.
(Notes for Reality and Faith)