The following was in a letter of agreement at NWA from 1989 through the last contract:

6. Departure without at least one (1) functioning autopilot shall be at the captain’s discretion. Every effort will be made to effect repairs at the first maintenance base.

From what I read in the original post, it sounds like the Captain made a good decision. This is not a contest to see how great a pilot you are because you've flown without an autopilot before - this is about safety. Apparently the pilots at Northwest thought it important enough to include it in their contract for years.