Your choice of twin primes as an example is kind of odd; implicitly, we are discussing the cluster of ideas that are controversial in some ideological sense.

To be clear, I agree that ideas often spread for reasons other than their truth. I agree that because of this, if you are careful, you can use the history of religion as ancillary evidence against theism.

But in general, you have to be really, really careful not to use "memetic effects" as just another excuse to stop listening to people (LessWrong's main danger is that it is full of such excuses). Sometimes true ideas spread for bad reasons. Sometimes what looks like a bad reason appears so because of your own ideology.

I'm not saying become a theist, or read huge treatises on theology. I'm saying give theism the 5 minutes of serious consideration (e.g., listening to a smart proponent) owed a belief held by a very large fraction of the planet.