I would not trust the flight crew, as they can not see the actual situation or like in the Iberia case obviously choose to ignore it.
I would inform a CC member and ask him/her to relay it to the cockpit.
If they choose to ignore it again, I would start praying loudly.
I remember an ATR charter a couple of years ago carrying Ford Engineers and suppliers back from Milan to CGN after a day at the EMO machine tool show. Their plane crashed, nobody survived. The other one I remember was a Citation taking off from ZRH on RWY 34 to BRN. PIC decided against deicing in order to get into BRN before the night closure. Again no survivors.
Frank