What a dreadful article. It was fact free at best. We saw mist/condensed vapour coming from the side panels and coughing passengers. It's not normal but we also don't know what created it. It certainly was not the Captain as aircraft air-conditioning systems do not have a "mist/fog" selection. Rather boringly, it's OFF/ON with temperature selection (the latter is often made in the cabin) and there might even be an ECON selection. It is possible that there was a fault in the water separator or even in the ground supply. Or there again, the air outside could have been so humid that no system could remove sufficient water to prevent misting.
PM