Side note: "Religion is the opiate of the masses" is often (falsely) attributed to Karl Marx, who actually had a much more nuanced understanding of religion.

 "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." 

(The opium reference is from an age with no cheap synthetic painkillers, and a lot of untreated health issues. There was not the reflexive stigma attached to it that we have today).