Wow, this really made me upset. Don’t worry about people like this man, they shouldn’t treat you like that. You did your best and that’s all that matters. I would however email HR like the other person said as someone shouldn’t be treating you different just because you stutter. Keep your head up man, you’ll get a job if you keep applying. I recently struggled with my stuttering through a phone interview and was still offered a position. Keep your head up man I know it’s tough, you just gotta stay strong. Better days ahead.