This is more of a who to believe situation clearly favoured by the conditions of weather at that moment.
If like LTD says forms of snow where clearly being built in the wing surface then very bad for the IB capt. But what if the IB capt did check their surfaces, you normally check the upper wing from inside the passenger cabin, and as they had also recently refuelled the warming up of the fuel gives a temperauture exchange that is also to consider. As LTD said; it started snowing at that time!
what to be believe now or not is if the snow didnt adhere to the surface and just melted down as it would normally do after you refuel or if there was clear deposits after just a short time of snowing. Snow doesnt build up in surfaces with temperatures over 3-4º and after refuelling I dont know what temperature you have but I do think is above that. Another story is if they refuelld long ago,, or it started snowing some time ago.
Nevrtheless safety is first and with the doubt always act in accordance, and having heard the link(very good one there) I dont see a lot of arrogance in the way of saying it, except that maybe he could have called the IB pilots attention in a more of a colleague way as we should all be, and tell him what hes seeing, after all you are never gonna get told off for that.