I'll just put as much time and delay between each letter as possible (by responding to a letter immediately upon receiving their next letter, and repeating that procedure regarding the newly received letter, until I can finally inform them that the statute of limitations is up). My latest letter warns that if they continue to accuse and harass me, I will write them up to the relevant authorities. And, I will do what I say. (I've already downloaded your letters... meaning Troy's letters... so that I have templates to work off of.) And, in my next letter they will get copies of the letters I've sent out to the authorities.
Mulligan's view on writing the attorney bar associations makes sense as they protect their own, except for egregious violations that they want to distance themselves from. Yet, letters to the FTC, BBBs, Attorney Generals, some big consumer advocate groups, and my own state representatives should have some impact.