If he hates his own name that much he should change it by deed poll!
It can be very hard to get out of calling someone a name that was lovingly chosen and that they've been know as by relatives since birth.
One of my siblings was always known as "Corin", their full Christian name, until they were 30+
They moved to another country where their spouse came from, overnight developed a completely different accent and everyone over there started calling them Corrie because the inlaws didn't like Corin. But in their dialect it sounds like Curry.
Curry/Corrie also has a complete different personality to the person we grew up with - it's like they emigrated, changed their name, social class, personality and adopted this new persona. I was only little at the time and it was a really uncanny valley moment when my sibling came home, acting strangely with a fake accent and new name and we were all saying, "why are you being like this? Are you going to drop it and be normal now?" It really seemed like a weird act and everyone assumed it was a joke.
Old school friends who meet them now after not seeing them for decades look really uncomfortable as if they are thinking the same thing (and still call them Corin). At a recent funeral our cousins approached us afterwards and asked if it was a genuine accent/personality or if they were taking the piss. It really is bizzarre.
We already have a Corrie in the family of the opposite sex and previous generation.
It's been very hard to get out of the way of calling my sibling Corin, because that's their name and had been their name for 30+ years and we already have a well known and loved character of a Corrie in the family. Their kids and spouse obviously find it weird that everyone on our side of the family still calls them Corin instead of Corrie(Curry) but we find it equally weird that the in laws decided to rename our sibling/parents' child. Our parents were actually quite hurt at the time. There was a lot of thought that went into Corin's name and they were named after someone special that saved our mother and Corin's lives during a challenging pregnancy and a difficult birth.
And my sibling doesn't seem to mind that we still call them Corin, it's more their spouse/in laws and kids that look at us weird. If my sibling did kick up a fuss or pass comment, they'd be given a very short shrift. They've called me a detested shortening of my name for the past 40 years that no one else uses and they know I can't stand. At least we call them by their ACTUAL name.