Upvote:3
Here are some of the reasons I've heard:
In her book Seeking God, Esther de Waal summarizes an aspect of Benedictine (communal) life: the community fundamentally exists for the benefit of the individual, and not the other way around. Yes, the individual contributes to the community, and yes, the individual serves other members of the community, but if these did not serve the purpose of increasing an individual's holiness, there would be no point.
Christians, based on Genesis, consider all people to be made in God's image and thus worthy of certain things for their own sake. The idea of individual dignity seems to be absent from communism - instead the emphasis is on the workers as a group.
I heard a talk from (now Bishop) Robert Barron (can't find the mp3 online anymore unfortunately) where he discusses the Catholic Church's teaching on social justice. He discusses the works Rerum Novarum and Centisimus Annus and in particular he cites this passage from St John Paul:
Returning now to the initial question: can it perhaps be said that, after the failure of Communism, capitalism is the victorious social system, and that capitalism should be the goal of the countries now making efforts to rebuild their economy and society? Is this the model which ought to be proposed to the countries of the Third World which are searching for the path to true economic and civil progress?
The answer is obviously complex. If by "capitalism" is meant an economic system which recognizes the fundamental and positive role of business, the market, private property and the resulting responsibility for the means of production, as well as free human creativity in the economic sector, then the answer is certainly in the affirmative.
There are probably others, but the above are a few common ones.