Real-Life Decision Making -- Solution
You accept the client's decision.
You tell the client you appreciate his concerns, and that you will find another candidate. You fill the opening by the end of the week.
You never tell the individual with Parkinson's disease about the position. Over the next few months, you recommend him to several clients seeking qualified computer professionals. However, each time the issue of the candidate's illness comes up, the client refuses to consider hiring him.
The candidate often calls to ask how things are going. At first you stall and tell him there are no openings in his particular area of expertise. Finally you admit that the problem is his illness. The candidate becomes frustrated and convinced you're not trying hard enough to "sell" him to your clients. He accuses you of being concerned only with your client's needs.
After six months, the candidate calls to say that he has signed on with another recruiting firm that specializes in placing disabled individuals. He makes a point of telling you that he is still symptom-free.
The entire incident leaves a bad taste in your mouth. Your reputation probably won't suffer any lasting damage, but you haven't made any friends, either. And you're at a loss to know how to proceed the next time you're approached by a "problem" candidate.