Having flown in the Arctic and after having many hours of cold weather operations, I agree with what has been said. First of all, there is a legal issue that has been stated. Secondly, there is no such thing as a little ice that you can safely go with. Hoarfrost on a wing is not acceptable as the airflow is disturbed as it passes over the wing. The net affect is increased stall speed and no margins for maneuver. There have been many precedents set from guys that have taken off in iced up, frosted up aircraft. Sadly, they are not here to tell us their story. We can only read about their mistakes in safety investigation reports.
You did the right thing. Complements of the season, you are here to talk about it.