What is schlesinger worried about in this passage?

Schlesinger is talking about the "mass organizations" of the communist parties. Those were actually fronts for the communist parties that would, many times, attract members that were not aware of the political agenda or political mindset of the leaders.

This is a strategy commonly used by communist parties around the world and it's very prominent in South America, specially.

Schlesinger's concern is about the influence that the Communist Party had over those groups and how its power was increasing through groups that "disguised" as something else but were actually under control of the Communist Party and the party could eventually use the individuals that belonged to those groups to achieve their goals and many times, the individuals used wouldn't even be aware of it.

to reform the distraught soviet union, the democratization of the communist party was promoted through party secretary mikhail gorbachev's policies of “perestroika” and “glasnost.” perestroika refers to the reconstruction of the political and economic system established by the communist party.

barrio is a spanish word meaning neighborhood. in spain, several latin american countries and the philippines, the term is also used officially to denote a division of a municipality while a ghetto is a part of a city in which members of a minority group live, typically as a result of social, legal, or economic pressure. the term may have originally been used in venice to describe the part of the city to which jews were restricted and segregated.