Apparently, the MPI people do read the boards, so I'm guessing that they're picking up on dissatisfaction with the plans for the pre-Barnabas episodes on DVD. However, the MPI rep did write that plans have not been finalized, so perhaps they're just testing the waters.
I'm not sure if petitions do any good. My suggestion is to write a calm, carefully worded letter of complaint to MPI. Written letters sent by postal mail are probably the most effective because they require a bit more effort than an e-mail and, therefore, carry more weight.
Also, accosting the sales reps at the Fest most likely will not help matters. I suspect that the people MPI sends to the Fests have very little executive power.
The key is to express dissatisfaction in a calm, reasonable manner to the people who make these decisions.