Because the BBB protects their members. How can they be impartial when the other party is a member? I have dealt with the BBB in the past and had to tell the BBB their policy. It has happened more than once and the other party was a BBB member. Think about it, why would they continue to be a BBB member if they had a poor rating? The BBB pays their bills because of those membership dues. Why would they bite the hand that feeds them?

You file a complaint agains the MB dealer and they are going to claim the vehicle had a 60-day warranty and it lapsed. You also bought a used vehicle that was sold AS IS and they are not responsible for any issues.

Just wait and see.

Also, did you check the BBB rating before you went to the dealer? Didn't think so. Does a BBB rating even matter? The only reason why some places like them as it gives fools a warm and fuzzy feeling.