Please remember that this is a forum of a very big group of participants with varying points of view and resulting opinions.
Even if he was previously a person that said golang doesnt need generics, I struggle with your point of view. It seems you're of the opinion that nobody should be allowed to... change their opinion? Or at least has to be continuously told that they're dumb because they held an opinion that turned out to be incorrect? We're all people and make mistakes/have incorrect assumptions about topics, why not just accept that and move on?
You might want to refocus on what kind of person you want to be, because both of your comments come off as very hostile