From Peter Hitchens' thoughts on his brother:
"Liberal world reformers make the grave mistake of thinking that if you abolish a great force you don’t like, it will be replaced by empty space."
Human nature cannot be changed, no matter how many diplomas are held by the members of the committee decreeing the improvements. One irrationality is simply and inevitably replaced by another. The difference is that the original irrationality, which has been around for thousands of years, is by now mostly harmless and may even have a social importance we cannot immediately understand, whereas the new irrationality will more likely than not turn out to be quite dangerous indeed.
UPDATE: I must link to an old post from Asymmetrical Information. This is probably my favorite blog post ever, and may be one of the greatest essays on conservative thought there is (really!). I used to be more libertarian than I now am, reading this was a major factor in that change. So please do read the whole thing!