I have been managing a direct report, whom I inherited, for several years now. The person works in a position where he must have excellent writing and communication skills. Writing and editing other people's work is a large part of the job. It's not all we do, but it is a part of our daily work, and we are in a small team where no one can be exempt from this job requirement.
English is this person's second language and he makes consistent grammar errors. I have given extremely specific feedback about this to him on many occasions, and it's been part of every performance review, but the same exact errors are part of his every communication, both written and oral. He recently asked for a promotion and I realized that unless he works on this, I don't feel comfortable supporting it. At first, he seemed willing to work on this, and even to go for tutoring, but then he started saying he feels "singled out" and even discriminated against, and that my feedback is causing him a lot of stress. He even flat out said he disagrees with me that he needs to work on his grammar, and that I am "wrong" that he needs to work on it (really an insubordinate statement). This is after I yet again sent him numerous, specific examples of the errors he is making in his writing. I am concerned that he is making errors on our clients' work.
At this point, I feel stuck. I think I have to do a Performance Improvement Plan with a deadline on it, and if the person refuses to get help with this area of his performace, he has to be let go.
I have reviewed job descriptions of many similar positions at other organizations and they all state that excellent communication skills, and even excellent grammar and spelling, are essential job requirements. Therefore, I don't believe I'm discriminating here.