The most painful moment was when I had a close friend almost enjoy the fact my wife had a miscarriage. It was completely insensitive and made me realise that I have no interest in being friends with someone who is willing to compete on something so ridiculous.
Lots of thinking later, and I can now tell the difference between acquaintances and friends. There’s a simple test: acquaintances will be there when you want them to; friends will be there when you don’t want them to, but need them to anyway. An acquaintance would never do that.
Learning to disengage or set firm boundaries in situations where that is happening is one of the most powerful and healthy things one can do.
And you can and should still absolutely cut them out of your life. Let them have each other.
There’s a reason misery loves company.
Additionally, it is normal to accept derisive talk (= banter) from good friends. If a friend doesn't get a promotion, you can be very humoristically negative about it in way that would in no way be okay with a stranger.
So yes, in those ways it is normal to enjoy watching your friends mess up, and it is normal to feel more at ease with it with friends rather than strangers.
However, it is not normal to enjoy seeing your friends fail in life, at all. That goes way beyond schadenfreude and even narcissism, straight into sociopathy.
I think this is just him trying to justify it.
One day, a friend told me about how a founder he knew had raised a round, and I said something like "damn, it's always everyone else" and my friend went "why not just be happy for them? It's not like they're hurting you".
That's when I realized that yes, I could just be happy for them, and that they indeed didn't hurt me, and that I could just be making this an overall happier event by being happy.
Since then, I'm genuinely happy when anyone wins, to the point where I'll complain to people about something that happens to me, they'll say "well if it makes you feel better, that happened to me too", and my response is "why would it make me feel better that my friend also had this bad thing happen to them?", which gets some puzzled "you're right" responses.
I think it is widespread that people feel like this, hence the "if it makes you feel better" response. I think if your friend understands that this isn't a great way to feel, it'll all be OK.
Sometimes people feel alone in their failures. Knowing that something similar has happened to others can help the person feel less alone.