It's OK OP. Honestly, we've all been there, me included. I remember I had an interview for the government a while back. It was a disaster. Stumbled over every question, very severely too. It was horrendous. That interviewer can eat shit and die! Just imagine how this ass would have treated you on the job. Keep fighting man. Like I said, I'm 99% positive we've all had shitty interview experiences here. They will improve given time.