What made it even worse was the "there's no time" remark when Jon asked him to come with. Guy just sauntered off and got killed instantly. I'd understand if he was holding off the army creating a diversion but he just walks to his death. Lol.
So that's where Jon gets it from. Why fight off the undead near the dragon as it evacuates people when you can walk onto the ice and fight them there? Makes total sense.