A lot of the advice you have been given here is sound. Had some experience of helping people with this kinda thing before and what really hacks me off is that managers/flt cdrs/whatever don't apply the correct processes. If someone is C
p (not saying you are Ooops), fine, then try and help them out, give them every opportunity to improve and make sure they know what is wrong as early as possible.
This is where mid-terms etc are so important, they provide an opportunity to be really open about what someone needs to improve upon to get the sort of F6000/OJAR they want/deserve. If all that help doesn't work, then there are the formal processes to follow (Informal warning, formal warning, admin discharge etc), but it all HAS to be evidence based. If there is no evidence they cannot write it, or take it further.
Oops, if you are not happy, fight it. Best to find someone to bounce the reply off before you send it as these things need to be non-confrontational, non-personal statements of why something is incorrect.
Good luck