Sort of NAH? The interviewer is an asshole for sure but

Neither you nor the job agency are assholes.

You know your side so I won’t go into that. But the job agency is likely called by people who just need quick cogs in their machine, they look to place people who need jobs in jobs ASAP. The interviewer might not be interested in applicants through that agency anymore, and while you are happier to continue your job search others might not care and just need the job now. If you get interviews through an agency you are now representing you and that agency, and it makes sense that they ask that you do not suddenly end interviews. When you represent only yourself you have more freedoms, but less connections.