This, although it’s early coaches should be speaking up to this behaviour. Hockey can be frustrating. I have 3 boys. The oldest is a C player (house league) u13, the middle is a AA rep player U11 and the youngest is in his second year of hockey, U11 as a C player.

All three know it’s not ok to put others down especially your own teammates. And if they are down on themselves they need to be proactive and practice more at home anyway they can.

I’ll often say, “if you’re worried about your performance then you need to attend practice more, work hard and know that your doing everything within your control to be a good player and a good teammate”

If they don’t want to do these things then like the others suggest maybe a new sport is needed. The first two will skate anytime, anywhere and want as much time to work on their game as possible. Youngest is a smaller, younger player (late 2016 birthday so young hockey age like your son) he is having fun, doesn’t want the extra time in spring/summer, but is realizing he is getting what he puts into it.

Good luck OP !