If religion is the opiate of the masses

Not that I disagree with the rest of the comment, but this is constantly misquoted - it's not so direct in the non-truncated version.

Religious suffering is, at one and the same time, the expression of real suffering and a protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people.

It's more talking about how religion is a reflection of material conditions.