Q: Didn't Adm. J.O. Richardson get fired because he said that the fleet was vulnerable at Pearl Harbor to surprise attack?
A: Richardson's complaints were logistical in nature, not tactical. He testified before the Congressional Hearings (Pt. 1, p. 253-340):
Mr. Mitchell: Well, you had developed by this time very definitive ideas in your own mind in opposition to the advisability of basing the fleet at Pearl Harbor, had you not? Will you please state in your own way just what the situation was and what your objections were grounded upon?
Admiral Richardson: My objections for remaining there were, primarily, that you only had one port, secure port, and very crowded, no recreation facilities for the men, a long distance from Pearl Harbor to the city of Honolulu, inadequate transportation, inadequate airfields.
A carrier cannot conduct all training for her planes from the carrier deck. In order to launch her planes she must be underway at substantial speed, using up large amounts of fuel. So that wherever carriers are training their squadrons there must be flying fields available, so that while the ship herself is undergoing overhaul, or repair, or upkeep, the planes may conduct training, flying from the flying fields.
There were inadequate and restricted areas for anchorages of the fleet; to take them in and out of Pearl Harbor wasted time.
Another reason, which was a substantial one; Americans are perfectly willing to go anywhere, stay anywhere, do anything when  there is a job to be done and they can see the reason for their being there, but to keep the fleet, during what men considered normal peacetime, away from the coast and away from their families, away from recreation, rendered it difficult to maintain a high state of morale that is essential to successful training.
For those reasons, and because I believe that the fleet could be better prepared for war on a normal basis on the west coast, I wanted to return to the west coast.
His testimony quotes a letter dated September 12, 1940, in which he lists these points:
Retention of the fleet in the Hawaiian Area:
(a) From a purely Naval point of view there are many disadvantages attached to basing the fleet in this area, some of which are:
(1) Difficulty, delay and cost of transporting men, munitions, and supplies.
(2) Inadequacy of Lahaina as operating anchorage due to lack of security.
(3) Inadequacy of Pearl Harbor as operating anchorage due to difficulties of entry, berthing and departure of large ships.
 (4) Congested and restricted operating areas, in the air and on the surface.
(5) Inadequate facilities for the fleet services, training, recreation and housing.
(6) Prolonged absence from mainland of officers and men in time of peace adversely affects morale.
(7) In case of war, necessary for fleet to return to mobilization ports on West Coast or accept partial and unorganized mobilization measure resulting in confusion and a net loss of time.
Note that Richardson characterizes Pearl Harbor as a "secure port".