I had a similar issue many years ago with a plane load of upset pax because I would not depart in the middle of a snow storm when the national carrier had just taken off. Same Aircraft type, same destination, same half an inch of snow all over. Needless to say the airport did not have deciding fluid. I explained to the pax that the speed limit in the motorway is 120, some cars shoot pass at 150. Are they going to die? probably not. Nevertheless the limit is 120 and that is the speed I travel at.