As the right wing degenerates
There is no good reason why a firm anti-jihadist such as Charles Johnson should ever have needed to identify with the right in the first place. Islam is at least as much of an enemy and menace to freedom, secularism, progress, and all the other values of liberal civilization as the Christian Right is; they are both theocratic totalitarianisms.
Andrew Sullivan has a similar, somewhat longer reflection.
Both emphasize that their own views have not changed much; it's the right itself which has devolved into insanity.
Johnson: "The American right wing has gone off the rails, into the bushes, and off the cliff. I won’t be going over the cliff with them."
Sullivan: "To paraphrase Reagan, I didn't leave the conservative movement. It left me."
Indeed, it seems to have left objective reality behind entirely.