That's true. I mean he did argue the fact that he's a variant of SA to many.
Nonetheless, I just don't think it's Kale's character, he has always been quite honorable.
Also, it would alienate most of the friends he's built up. Would just be a bad move.
Even more so because where as Kale before had no qualms with Astroism and was actually quite the friend and ally to the religion (indeed only seeing it as a variant of his own) he is now bitter and feels betrayed and that the Church has shown its corruption.
Psh... it's not corruption. Change your point of view; see it as an opportunity!
Besides, the friends Kale has built up are mostly pretty much worthless, or rapidly converting to Astroism, or already there.
ONE OF US. ONE OF US.