That doesn't say you need doors... it says you need to maintain your vehicle in working order. The entire law is about maintenance... no protrusions that could harm a pedestrian (can't be Mad Max)... that the door and hood hinges / latches be maintained so that the doors don't fall off while driving down the freeway and hurt someone. Sounds like you just pissed off a cop who was looking for BS excuse to pull you over and give you a hard time. Don't portray it as anything more than that...From the Olympian with State Patrol officer interpretation. I'm not trying to argue. The Law is the Law. Is it enforced is another issue.
RCW (Revised Code of Washington)