Commentary President Joe Biden, in his address to Congress, repeated his absurd claim that white supremacism is “the greatest” threat facing the country. He then proceeded to promote the defamatory mythology solely responsible for the recent disturbing rise in white supremacism. This truly dangerous incoherence requires a bit of unpacking, beginning with some simple definitions. What is white supremacism? The answer is hardly subtle. It’s an ideology that combines two fundamental ideas: “whiteness” and “supremacism.” Both are rooted in the notion that humanity divides into distinct groups based upon inherent characteristics. Supremacists believe that one group is superior to all others and thus uniquely qualified to rule. It’s an idea as old as history. Nazism, apartheid, the Ottoman millet system, and Jim Crow were 20th century supremacist systems. Today, Islamists preach Islamic supremacism, Louis Farrakhan prefers an Afro-centric supremacism, and the Chinese Communist Party is heir to a long line …