This is an interesting letter.

The obvious questions come about because of the details, or lack thereof, within the letter.

For example, when did this incident occur? You stated you purchased a 2003 model, but this could have been purchased used, recently.

You never state whether the problem was covered under warranty. You state in one of your replies that you are going to another service center, but may still have it denied under warranty coverage. As such, it is peculiar that you have not detailed the problem with the vehicle or requested it should be covered under warranty. As such, one would surmise that the problem was not allowable under warranty and you were not concerned about it being covered as such.

Taking this into account, is it possible that you were heated when addressing the sales manager? This may have been the reason that the service manager felt obligated to get involved.

I really do find it interesting that you chose not to contact the police about such an assault, but are asking for the service person to be fired.

Overall, this letter leaves more questions towards the letter writer. Overall, it presumes a lack of credibility.