It is leftism.
Most people do not recognize what is probably the single most important fact of modern life. One reason is that leftism is overwhelmingly secular (more than merely secular: it is inherently opposed to all traditional religions), and therefore people do not regard it as a religion. Another is that leftism so convincingly portrays itself as solely the product of reason, intellect, and science that it has not been seen as the dogma-based ideology that it is. Therefore, the vast majority of the people who affirm leftist beliefs think of their views as the only way to properly think about life.
That, in turn, explains why anyone who opposes leftism is labeled anti-intellectual, anti-progress, anti-science, anti-minority and anti-reason (among many other pejorative epithets): leftists truly believe that there is no other way to think.
How successful has leftism been?
It dominates the thinking of Europe, much of Latin America, Canada, and Asia, as well as the thinking of the political and intellectual elites of most of the world. Outside of the Muslim world, it is virtually the only way in which news is reported and virtually the only way in which young people are educated from elementary school through university.
Only the United States, of all Western countries, has resisted leftism. But that resistance is fading as increasing numbers of Americans abandon traditional Judeo-Christian religions, lead secular lives, are educated by teachers whose views are almost uniformly left-wing and are exposed on a daily basis virtually exclusively to leftist views in their news and entertainment media.
And when there is resistance, the left declares it "extremist." Merely believing that marriage should remain defined as it has been throughout recorded history, as between a man and a woman, renders you an extremist. So, too, belief that government should be small -- the Tea Party position -- renders one an extremist. Last week, the managing editor of Time Magazine, Richard Stengel, said on MSNBC that the Salafis, the most radical Islamist sect, are "the Tea Party of Muslim democracy."
Even Christianity and Judaism, the pillars of Judeo-Christian values, the moral value system upon which America was founded and thanks to which it became the world's beacon of liberty, have been widely influenced by leftism. Many priests, ministers, rabbis and many Jewish and Christian seminaries are leftist in content and Jewish or Christian only in form.