'Fuck Monsanto, and by association, fuck Cloudant' is not a constructive opening to a conversation. If that poster had started by saying 'This announcement makes me not want to do business with Cloudant. Here's why...' then I'd largely agree with you. You are right that Monsanto is a politically radioactive company, so putting out a cheery press release about becoming a core technology supplier displays a misunderstanding of branding.
However, raving and swearing at people is not persuasive, it's bullying. We'll never find out what pg really thinks of Monsanto or the idea of doing business with them, because all we've got is his understandably snippy reaction to what sounds like the aggressive ranting of an insane person.