If the dealership honestly believes that they are engaging in fair and honest business practices, they should not have any concerns with any actions the OP takes to broadcast those business practices, including social media, standard media or skywriting. On the other hand, if they're embarassed by their conduct, they shouldn't have done it.
And suggesting that the OP not Facebook or Tweet the experience because it may not be relevant to all, or even most, of her friends and followers? Well, I challenge abyone to find someone who only posts things relevant to all of their friends. I guess if all your friends and followers are a homogeneous group - like only my family and I only post about my family, that could qualify but I so not suspect that is the norm.