Not that I know of, at least for the fandoms I'm involved in.

I understand the need for people to vent, but mob mentality tends to run rampant at these secrets/hate comms, and the resulting sploogefest is never pretty, nor does it ever present an unpopular point of view in any kind of positive light. They're pretty much lacking any rational thought. It's better to just rant in your own journal, or in a fandom-appropriate comm.