Every star or other massive body in the universe rotates, if only a little. If such a body collapses, its spin, any spin at all, and thus, angular momentum approach infinity as r approaches 0. Angular momentum must be conserved. In order to produce a true singularity or a non-rotating black hole, there must be some process by which ALL angular momentum (energy) is dissipated or converted to something else.
Is there such a process? Otherwise all black holes must rotate, perhaps too fast or too slowly for us to detect, but they must rotate. Am I missing something? I've never heard this discussed before.