Its because even though he is dead, he is still one of their strongest enemies. His words live on in his books, articles, and videos available on Youtube. People can read and listen to his powerful defenses of free market capitalism, and his influence lives on.
Which is why Naomi Klein did her best to smear his name by trying to blame him for the worst abuses of the Pinochet regime, though he and his Chicago Boys had no real influence there till three years after the coup, long after most of the abuses actually happened.
Now Krugman and a few other Keynesians are trying to claim he was on their side. Of all the insults, that's hitting below the belt!
From A Lovefest Between Milton Friedman and J.M. Keynes by Nicholas Whapshott:
Yet Friedman’s contemporary supporters no less than his critics will be surprised to learn that he was in fact an enormous admirer of John Maynard Keynes—the patron saint of the New Deal—and not at all the absolute opponent of big government he is usually presumed to be.
Yet in his buried essay on Keynes, Friedman expressed a more complicated view. Abruptly dismissing Hayek’s notion that big government tends to curb the rights of individuals, Friedman reports that in Britain, where government was administered with integrity and honesty, governments have grown large without endangering the public good.
Where did he get that impression? Sounds to me like Friedman is saying the exact opposite, though maybe in a nice way so the publishers wouldn't be put off from actually including his essay.
Here is what Friedman actually said:
John Maynard Keynes by Milton Friedman:
The persuasiveness of Keynes’s view was greatly enhanced in Britain by historical experience, as well as by the example Keynes himself set. Britain retains an aristocratic structure—one in which noblesse oblige was more than a meaningless catchword. What has changed are the criteria for admission to the aristocracy—if not to a complete meritocracy, at least some way in that direction. Moreover, Britain’s nineteenth-century laissez-faire policy produced a largely incorruptible civil service, with limited scope for action, but with great powers of decision within those limits. It also produced a law-obedient citizenry that was responsive to the actions of the elected officials operating in turn under the influence of the civil service. The welfare state of the twentiethcentury has almost completely eroded both elements of this heritage. But that was not true when Keynes was forming his views, and during most of his public activity.
Notice that Friedman is saying that government can be good and incorruptible, bot only when it is limited. Clearly not an argument for BIG government, but limited government. It is the laissez-faire of the 19th century which made the SMALL government incorruptible, and the growth of government in the 20'th that corrupted it.
What is more, Friedman is saying that it is the incorruptible government of the 19th century that made Keynes thing that a big government could act responsibly.But small, responsible government doesn't mean big government can be responsible.