Some years ago when I was job hunting I applied for a position advertised by an agency. The position was on the edge of the space where I could be a good fit, and I was rejected. Few months afterwards the same agency advertised another position for which my profile would have been a perfect fit, and I applied.
The recruiter first contacted me to schedule an interview and asked me to provide some material formatted according to the agency standard. When I pointed him to the material I had already provided for the previous application, he wanted to cancel the interview as "I see now you have already been rejected by us".
I objected that the positions where considerably different and that I felt to be a better fit for the present one. The recruiter replied in a confronting way, and challenged me to send an impressive motivation letter for the position in half an hour, then if he was convinced he might change his mind.
I sent the motivation letter and was scheduled an interview with the agency shortly after. When I went to the interview I found out it was staged by this recruiter just as a practice session for a new hire of his agency to practice his interviewing skills. Then they communicated me I was rejected for not fitting the position.
Since the recruiter had slipped the name of the company in our mail exchange, I decided to apply directly to the company: I was called for an interview by them and was told I was their second best candidate for the position.
Few months ago the recruiter of the agency, through common contacts, has made a cold try to get me to work for his agency. I know I will be meeting him in person soon for a non work related event, and I am pretty sure he will make a direct attempt again.
How can I professionally tell him that I have no interest in working for an agency that, through his behavior, made me feel just like cannon fodder?