Regardless of the merits or otherwise of the de-icing, I'd say the F/O lost the plot when he decided to sue. Up to that point, the incident was relatively minor because nothing bad actually happened and it would most likely have disappeared into the filing cabinet never to emerge. Now it's major news and a lot more people in the industry know about it, which means that regardless of whether he wins the case or not, a lot of people will still point fingers. That is all self-inflicted.