Replay protection HF or SF? I am naively under the impression that just about anything can be a soft fork nowadays, and that this is one of the benefits of Segwit.  Also, it seems that many claim in order for Bitcoin Core to implement replay protection, a hard fork is required.  This seems contradictory.  Perhaps someone could correct any of these assumptions?
Replay protection is only needed in the case of a Hard Fork.

To understand why this is true you should first understand what HF and SF are.

A great answer on the difference of Soft or Hard Fork can be found here