I guess, there are two things now, one he has to believe all the initial words you spoke before the fight, as he's possibly feeling they were lies, as you tried to set things up that he would win...
Two anger plus over the other oponents response in public....his ego would be very low...I am not sure what to suggest there, other than you've done all you can...You may have to back off and just let what ever happens happens and maybe speak to his coach for your sake, to understand how someone gets past this...If not him, write to an experienced known boxer in compassion and ask their advice you never know, everyone has heart and maybe one will reply.
CW
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