The opiate for the people quotation in the context:

The struggle against religion is therefore indirectly a fight against the world of which religion is the spiritual aroma.

Religious distress is at the same time the expression of real distress and also the protest against real distress. Religion is the sigh of the oppressed creature, the heart of a heartless world, just as it is the spirit of spiritless conditions. It is the opium of the people.

To abolish religion as the illusory happiness of the people is to demand their real happiness. The demand to give up illusions about the existing state of affairs is the demand to give up a state of affairs which needs illusions. The criticism of religion is therefore in embryo the criticism of the vale of tears, the halo of which is religion.

Criticism has torn up the imaginary flowers from the chain not so that man shall wear the unadorned, bleak chain but so that he will shake off the chain and pluck the living flower. The criticism of religion disillusions man to make him think and act and shape his reality like a man who has been disillusioned and has come to reason, so that he will revolve round himself and therefore round his true sun. Religion is only the illusory sun which revolves round man as long as he does not revolve round himself.

from CONTRIBUTION TO THE CRITIQUE OF HEGEL'S PHILOSOPHY OF LAW

I fail to see that Marx was trying to say something positive about religion.

Wolfgang