As with many Liberation Theologians, the work of Gustavo Gutiérrez shares a number of similarities to Marxism. Marxists were at the forefront of anti-government resistance movements and campaigns for social and economic change in Latin America during the early years of the Liberation Theology movement. In due course, they formed a loose alliance with Liberation Theologians such as Gutiérrez to agitate for an emancipatory economic order that would address the long-standing grievances of the poor and dispossessed.
The Catholic Church hierarchy was profoundly uneasy at this development, and at the increasingly strident rhetoric behind Gutiérrez's expressed preference for the poor. Some senior bishops felt that he was becoming too close to Marxism in his analysis of poverty and other social evils in Latin American society. Opponents of Gutiérrez were quick to remind him that Marxism is an officially atheistic ideology, which regards religion as a tool of oppression used by the ruling class to keep the proletariat in a state of permanent subjection.
However, it's notable that the Catholic Church never formally censored any of Gutiérrez's opinions. This was largely due to the fact that his use of Marxism was purely instrumental, a useful analytical tool for understanding some of society's most pressing problems. At no point did Gutiérrez have the intention of working towards a Marxist revolution. He simply wanted to build a new society based on a "preferential option for the poor," which he believed was perfectly in line with the dictates of both Scripture and Church tradition.