If what you say is true, why have so many religious sf stories come to be considered classics? I'll only mention Blish's A Case of Conscience, Miller's A Canticle for Leibowitz, and Lewis's Out of the Silent Planet.
Yes, religion is the opiate of the masses. But you just try to take an opiate away from someone who is addicted, and watch what happens. All science can offer is comfort and long life -- in a universe that will eventually suffer heat death and the end of everything. Religion offers love and eternal bliss. Which would you choose, if you were not educated enough to tell the true offer from the false?
Religion belongs in sf because it is part of human nature, and everything human is fair game for sf writers.
