So many things about past presidents have been controversial but they're not accepted as truth until after the fact. Even if the truth were known by some, it takes a general public that is willing to listen for it to accepted as truth at the time. In order for the general public to be willing to listen, it's going to take someone to tell them whom they are receptive to.
It was explained somewhere that because republicans are now perceived as running a negative campaign, if anyone in the McCain campagin or even any republican were to make this an issue, just the fact that a republican would be making it an issue would make the issue meaningless in the eyes of the public. In order for the public to listen and to understand the seriousness before it's too late to matter, it's going to take a democrat to say it, otherwise it will fall on deaf ears and it won't matter except in the history books after all is said and done.
Fortunately Philip Berg is someone that the general public is more likely to listen to because he is a life-long democrat, and it's likely that in order for his points to be received more effectively by the public, republicans may have to lay low for a bit so that there is no interference in the most likely form of initial acceptance to the public.