One is the yearning for utopia. Since Marx, the left has sought utopia in this world. And that means constantly transforming every aspect of society. As then-Senator Barack Obama said prior to the 2008 election: "We are five days away from fundamentally transforming the United States of America."
By definition, those who seek to transform consider the old essentially worthless.
The other answer is self-esteem. The left began the self-esteem movement in large measure because of its own high self-esteem. Those on the left are certain that they are smarter, kinder, more moral and more compassionate than -- in every way superior to -- their opponents.
That is a major reason for the left's problem with the old: If the old is great, then they and their new ideas are probably not that great.
Just about everyone who is not on the cultural left knows that all the great masters were incomparably superior to Jackson Pollock and other 20th-centuries artists who produced meaningless and talentless art. And because there are so few artists at any time who measure up to the old standards (standards that are synonymous with standards of excellence), the old standards have simply been abandoned.
This applies equally to morality. The left doesn't want to be bound or answerable to a higher moral authority. Rather, one's heart and reason are the best moral guides. Here, too, the old codes, especially as embodied in traditional religion, must be overthrown.
Prior to the ascendance of the left, it was assumed that the old had more wisdom than the young. Indeed, even every leftist I have asked, "Are you wiser today than 20 years ago?" has answered in the affirmative.
Nevertheless the left has transformed "old" -- a title that commanded respect in every civilization prior to the pre-1960s West -- into a pejorative.
As a result we live in the age of new music, new art, new families, new morality, new education, and now new marriage. If you think all these are good, then "old white males," like almost everything else old, do indeed constitute a threat. If you think the left's belief in "new" and "change" hurts society, "old" sounds good.
Dennis Prager is a SRN radio show host, contributing columnist for Townhall.com and author of his newest book, “The Ten Commandments: Still the Best Moral Code.”