they are requesting you to remove the posts on forums?
What authority are they basing on to require you to do that? What I can think of is defamation, but since that doesn't seem to be the case, and they continue to refuse service for your car I think you can ignore this request.
Now back to the main point, based on what you said and the observations from other members, it's most probable that it was due to their negligence that you almost got yourself killed.
I'd say I agree with some of the comments above, contact media, BMWNA, and as a last resort a lawyer. But I wouldn't go down the lawyer route until BMWNA refuses to do anything. I would additionally request for this dealership to be closed down.