.. from the "Rumor Has It" website Snopes:
It has become fashionable to portray outdated societal behaviors and attitudes — ones we now consider desperately wrongheaded — to be worse than they really were as a way of making a point about how much we've improved. When we despair over the human condition and feel the need for a little pat on the back, a few startling comparisons between us modern enlightened folks and those terrible neanderthals of yesteryear give us that. We go away from such readings a bit proud of how we've pulled ourselves up by our bootstraps and with our halos a bit more brightly burnished. The juxtaposition of wonderful modernity with a tawdry past also serves to reinforce the 'rightness' of current societal stances by making any other positions appear ludicrous. It reminds folks of the importance of holding on to these newer ways of thinking and to caution them against falling back into older patterns which may be more comfortable but less socially desirable. Such reinforcement works on the principle that if you won't do a good thing just for its own sake, you'll surely do it to avoid being laughed at and looked down upon by your peers.