To rebuild your confidence in himself isn't going to be easy, but slowly and surely with an amazing amount of positive reinforcement in everything they do, is a start. To try and remind him that in his case there is no I in team, and he cant win a match on his own, he is alone in the goal, but there are 10 other players on the pitch, so conceding isn't solely his fault. Because he is part of a team and it doesn't matter whether the team wins, loses or draws, they all, win, lose or draw and remid him that his coach is predominantly at fault as he is the coach, and he has been taught and supposedly learnt how to coach, teach and safeguard everything football. Because the clubs dont care about safeguarding, the governance should be stricter, we are there to support the kids, to make it a safe space, we are their to protect, nurture and coach the young and vunerable. I hate and dispise idiots that call themselves coaches, you dont deserve the position if your going to loose it. I'm so sorry that you both had to go thought that, I would make a complaint to your local FA and seek advice from your local police service, as verbal abuse has no place in society, to start Personally, to show the person that he has no right to talk to anyone like that.