One common mistake that many employees make, when they are accused of some kind of misconduct or violation at workplace is overreacting and otherwise going way too far to defend themselves prematurely, which often makes their situation worse than it would otherwise have been. This exaggerated reaction might include sending nasty e-mails or even screaming at the employer due to the frustration of being accused of something you haven't done, running to EEOC to file a discrimination charge, even though there is no evidence whatsoever that the false accusations are due to any kind of unlawful discrimination or retaliation, resigning or taking any other relatively drastic step. These types of aggressive actions do not benefit the accused, but only increase the chances of being further disciplined or terminated. A much better approach is to cooperate with any kind of investigation into the accusations openly, honestly and respectfully without letting the emotions damage your reputation and your relationships with your co-workers or management any further. 

The video below talks about one very important tip for anyone who has been falsely accused of workplace violence or similar violation at and who is being investigated:

Receiving an unfair revaluation or performance review is a common and frustrating experience for many employees. And more effort you put into your work and the better you think you, do the more upsetting a bad review will naturally be to an employee, as he will feel unappreciated and set up to fail. However, in the absence of evidence that the real reason for the fact that you received a negative performance is discriminatory (i.e. due to age, race, disability, sexual orientation, national origin, religion, filing a workers comp claim, familial status, etc.) or retaliatory, there is not much you can legally do about it. Your employer is entitled to their subjective view and evaluation of your performance, however unfair and unjustified you believe your performance rating is.

If your performance review has been affected by a personal conflict with your management or by some other fair or unfair reason, again - it has no legal relevance in the absence of evidence that discrimination or retaliation were in play. ​The fact that the negative (unfair) performance review affected your psychological help, ability to focus and ability to sleep also has no legal relevance, as these are your subjective symptoms to the employer's conduct that might be unfair but not illegal. 

There are different ways of dealing with negative performance reviews, depending on the overall nature of the business in your industry, your position at the company, your relationships with your immediate supervisor and higher management, the specific reasons for the issues in your evaluation from your perspective and from employer's perspective, and other factors. Sometimes, writing a rebuttal to the questionable review is a good idea, while more often than not it will likely be pointless or even counterproductive. In some situation, complaining about discrimination after receiving a bad review is a good idea, while in other cases it isn't.  Finally, in some cases looking for a new job is the only and the best option you might have. An experienced employment attorney should be able to advise you on the best legal and practical option for your particular situation. 

We review hundreds of documents and e-mails from different employees' personnel files every week. I am often amazed by the tone of some of  those e-mails from employees to their managers.  From accusations that the manager is corrupt, to long laundry lists of all the reasons that the employee believes his manager is not fit for his job.

When I read those types of e-mails, I can't help but ask myself - what was the writer hoping to accomplish by writing that e-mail? And that's the exact question you should be asking yourself before writing that kind of e-mail to your supervisor. Without knowing much about who you are and where you work, I assure you that sending an e-mail full of criticisms to your employer is not going to (1) make him treat you better or (2) get you promoted.  At best, it will cause some type of personal friction between the two of you, and at worst - it will encourage that supervisor engage in a campaign of retaliating against you, micromanaging you, writing you up and even trying to fire you. Whether it will be legal or not is a different story, and that will depend on what you complained about and other facts. But, the bottom line will remain the same - your supervisor will try to make your life harder regardless of what the law says about his actions. 

So, before you consider writing that harsh e-mail, consider (a) whether it's really worth sending and what the goal of that e-mail is; and (2) have someone else more "objective" review your e-mail before sending it out to make sure it doesn't appear more harsh than you really want it to be. Usually, unless you are ready to quit, giving your piece of mind to your manager has way more risks than benefits.