Marxist humanism is a very liberal (in American way) interpretation of the work of Karl Marx, especially the Paris Manuscript and his early theory of alienation.
Most of the authors whose books inspired liberal 1968 student revolt self-described themselves as Marxist humanists, e.g. Herbert Marcuse or Wilhelm Reich. Their new political movement called New Left shifted MarxistsMarxists' attention from class struggle towards social issues such as civil and political rights, feminism, gay rights, abortion rights, gender roles and drug policy reforms.
Freudo-Marxism borrowed from Freud the theory of conflict between the individual and civilization. Marxists attempt to liberate people by creating a non-repressive society.
Also, some liberal feminist movements are inspired by the unfinished book of Karl Marx published by Engels. The Origin of the Family, Private Property and the State
Marxism attempts to liberate people from work, culture, religion, and morality therefore it is a liberal ideology.