Dan Bobinski's Answer:
Unfortunately, this is one of the most frustrating scenarios found in the workplace.
At first glance, you have three options:
1. Remain with the status quo.. Lay low, absorb the pain, and remain uncomfortable.
2. Go over his head. He's the general manager, not the CEO. In other words, he reports to somebody. Perhaps pressure could be brought to bear from above.
Caution: I don't recommend either of these first two options. I recommend option three:
3. Rethink your HR strategy. When HR brought in the coach, they did what they thought was right. Unfortunately, you're still experiencing the problem! So first things first: Document-document-document. The hardest part of this is staying totally objective, writing only what you observe, not what you interpret.
Also, make sure you document specifics. Laura Crawshaw, in her book Taming the Abrasive Manager, says this is a vital starting point.
I believe Crawshaw to be the best authority out there on dealing with abrasive managers, so if she says to document specifics, that's what you should do.
You say he listens in on telephone calls - this is too general. What calls does he listen in on and when does he do it? You say he's a manipulating liar. How? What happened?
Identify the specific behaviors of each incident. Example: "He raised his voice" instead of "he got upset."
By the way, I highly recommend Crawshaw's book. You might also get one for your HR department. Then they'll understand what you're dealing with and have a better understanding of what they can(and should)do.
Here's the key: The group must maintain professionalism and squelch all emotional display. They must show total concern for the company's well-being, and above all, they must NOT threaten HR. Think of it as a low-key mass mutiny.
Start by saying how committed you are to the company's vision and mission, and emphasize that you all like working there that you want to help the company reach its goals.
Be sure to thank HR for their effort of bringing in the coach, but then present your observations (remember, no emotional dialog!) I can't emphasize how important it is not to draw inferences or interpret the GM's behavior. It's imperative you remain factual and objective.
Re-emphasize that you like working there, and you believe the GM wants the company to succeed, too. But add that his behaviors are no longer tolerable; that it's becoming a hostile work environment.
Also state that some of the people who brought complaints before have been fired, and that you're very afraid there's going to be similar retaliation (do not use the word 'revenge').
If it's true, you should add that you're heard others express concern about retaliation that people are afraid and that you don't want any retaliation for bringing these concerns to HR.
In short, don't demand or threaten. You create the best chances for change if, as a group, you express your loyalty to the company, provide specific examples of intolerable behavior, and state that you're afraid of retaliation for doing so.