But it took me a few weeks of swinging back and forth before I finally settled on Singularitarianism.

Here's a quote from an old revision of Wikipedia's entry on The True Believer that may be relevant here:

A core principle in the book is Hoffer's insight that mass movements are interchangeable; he notes fanatical Nazis later becoming fanatical Communists, fanatical Communists later becoming fanatical anti-Communists, and Saul, persecutor of Christians, becoming Paul, a fanatical Christian. For the true believer the substance of the mass movement isn't so important as that he or she is part of that movement.

And from the current revision of the same article:

Hoffer quotes extensively from leaders of the Nazi and communist parties in the early part of the 20th Century, to demonstrate, among other things, that they were competing for adherents from the same pool of people predisposed to support mass movements. Despite the two parties' fierce antagonism, they were more likely to gain recruits from their opposing party than from moderates with no affiliation to either.

Can't recommend this book enough, by the way.