Despite the warm glow of self-satisfaction that the liberal vision confers on liberals, ugly facts keep intruding to undermine that vision. Some liberals eventually jump ship and defect to conservatism when the facts keep piling up too high to ignore.
This takes time, of course, and in the meantime there is a never-ending supply of new young people to become charmed with the liberal vision and replace those who have become disenchanted with it.
Other liberals hang on to liberal ideas to the bitter end -- especially when the end is not that bitter for them personally, when they live insulated lives in academia, the courts, foundations and other places where there is no price for liberals to pay for being wrong, no matter how disastrous the consequences for others.
Still, facts are a danger to the vision. In recent times, those on the left have increasingly sought to suppress facts that go counter to the vision.
Research dealing with innate biological differences are of course anathema to those with the liberal-left vision. Even research that turns up cultural or other behavioral differences between groups is almost as great a danger.
Both kinds of research undermine the notion that there are "solutions" that government can impose to eliminate differences, gaps, disparities or "inequities" that liberalism claims to be able to eliminate.
Scientific research into differences in the way male and female brains function is denounced by radical feminists, who are calling for a ban on such research. No matter what the MRIs say, the radical feminists say all differences are due to "society."
Liberals have worked long and hard to get the very word "sex" replaced by "gender," since sex is an innate biological fact while gender is an arbitrary social designation, much as the French language assigns the female gender to the noun "plume" for pen.
It is a sign of how easy it is to stampede large sections of society that so many people now find it necessary to refer to gender instead of sex, even if they have not bothered to consider what the difference is or why they have changed what they say.
When it comes to racial and ethnic minorities, liberal politicians and judges can make it literally a federal case to give IQ tests to black children. Among the facts that we would never have known if some people did not find ways around this taboo is that black IQs have risen in recent times.
The greatest danger to the liberal vision are facts about the consequences of liberalism itself and the laws, policies, and ways of life that the left has spawned.
That the black family, which survived centuries of slavery and generations of discrimination, has disintegrated in the wake of the liberal welfare state is only one example.
Liberals have been driven to the desperate expedient of attributing this and other social pathology in today's ghettos to "a legacy of slavery" -- even though black children grew up with two parents more often under slavery than today.
Blacks only a generation or two out of slavery also had higher rates of employment and lower rates of crime than today.
The illogic of the "legacy of slavery" argument only illustrates the desperate attempt to salvage the liberal vision.
The very people who argue this way would never be guilty of such illogic in discussing something that was not such a threat to their vision.
One of the most telling examples of the social destructiveness of the left's welfare-state vision can be found among the white slum dwellers in Britain described in the brilliant and insightful book "Life at the Bottom" by Theodore Dalrymple.
There it is not possible to blame social degeneracy on slavery, racism or any of the other things cited as causes of the behavior and consequences found among blacks in American slums. Yet the results are virtually identical, right down to children beating up classmates for trying to get an education.
The vision of the left, full of envy and resentment, takes its worst toll on those at the bottom -- whether black or white -- who find in that paranoid vision an excuse for counterproductive and ultimately self-destructive attitudes and behavior.