“He was among the many students in the northern US who made the bus journey south to Montgomery, Alabama, organized by the Student Nonviolent Coordinating Committee (SNCC) in March 1965 to participate in the civil rights movement. This was during the time of but distinct from the Selma to Montgomery marches. He was jailed during the march and was allowed to make a phone call. Mamdani called the Ugandan Ambassador in Washington, D.C., for assistance. The ambassador asked him why he was "interfering in the internal affairs of a foreign country", to which he responded by saying that this was not an internal affair but a freedom struggle and that they too had gotten their freedom only last year.[11] Soon after, he learnt about Karl Marx's work from an FBI visit.[12]”

(http://www.autoadmit.com/thread.php?thread_id=5742968&forum_id=2#49053681)