Liberalism and racism
Liberalism is infamously renowned for perpetuating a system of race-based prejudice in societies where it has taken root. For instance, in the socialist and communist former nation of the U.S.S.R., the regime of Joseph Stalin, an avowed Marxist-Leninist and liberal enacted a policy of the deportation of the Soviet Jewish population to the far-eastern regions in Siberia, under a new puppet government, the "Jewish Autonomous Oblast". Those who did not cooperate with these laws and statutes were put on trial under the infamous "Doctor's Plot", the blatant racism of which shattered the communist sympathies of many liberals in the Western World. It is largely as a legacy of these policies which have forever stained the ideology of liberalism as a racist political system.
References: Joseph Telushkin. Jewish Literacy. NY: William Morrow and Co., 1991.