For the avoidance of doubt, I was putting that in the mouth of Hypothetical Modern-Day Karl Marx rather than expressing my own attitude to religion.

...ah. I completely misconstrued your intentions there. My apologies.

As for the use of religion in the Sequences, I think what's going on is this:

I think you are very probably correct, or close to correct. Unfortunately, it seems to have had the effect of turning atheism into something of an applause light in the comments.