Gentlemen.
Lets focus on the fact that the Society has been dumping chemicals at the farm. Marvin's information is still valuable because the whistleblower letter matches the news account. In my opinion this gives it some credibility.
I sincerely hope that this brother will come forward to the media about this toxic dump. As an "undercover brother" though I can appreciate the need for anonimity at times. Marvin's information in the past has been reliable, I see no reason to question the validity of it now.
SIAM