Answer:
Liberals consider that the lack of government participation in social and economic issues are what generate inequality, poverty and social backwardness in certain groups of the American population.
Thus, the lack of government participation to provide social welfare and regulate the inherent racism of African-Americans and other minorities is what in turn generates social exclusion, given that for reasons of discrimination they do not obtain the same jobs, opportunities or education as the white. This, as a consequence, generates poverty, inequality and pushes many of these people to the scourges of addictions, crime and other negativities.
Thus, racism and inequality are two issues that go hand in hand when explaining why many prisons are populated by people of certain races described as minorities in the country.