I agree with the previous responses, but I would add, not only put it down in writing but save it is a "draft" and give it a day or two or three, then re-read it and see if what you want to say to Corporate is really what you said in the draft. You want to be objective, not emotional, and sometimes, especially on what we say/type first off venting and not really objective. So in writing a letter to Corporate you don't want to come off as whinney. Just because your GM is a jerk, They already may know that, but be non-prejedicual ... What has he/she done to you and be professional, outling how there were threat, intimidation and bullying, that undermines productivity and what the the company stands for.
