What kind of causality would be broken if black hole singularities would be real?

In his article "The Universe as a Whole" 1, physicist Dennis Sciama said

We therefore face a crisis in theoretical physics. Either classical general relativity breaks down, or effectively negative energy densities can exist, or causality breaks down, or singularities exist in nature

Igor D Novikov developed his Self-Consistency Principle 2 to solve some paradoxes that arose from a certain type of causality violation. He said:

The only type of causality violation that the authors would find unacceptable is that embodied in the science-fiction concept of going backward in time and killing one’s younger self ("changing the past")

What kind of causality violation was Sciama talking about? Was it the kind of violation that produces paradoxes such as the ‘Grandfather paradox’? Was the kind of causality violation that Novikov talked about when he proposed his Self-Consistency Principle?