I get involved later on and say: ‘Christ this is horribly ugly code, how could you ever accept this?’

That’s a direct example of him acting like the smartest man in the room, and letting you know, straight from the link that was provided. He’s most likely right, but there are ways of stating that diplomatically. That’s not matter-of-fact, that’s just being arrogant. If you can’t see that, and you also find that people consider you arrogant, maybe you should consider talking to a professional about that.