I had this arguement with Sheldon Brown. Even if you have a perfect pedal stoke, you will still move imperceptibly from side to side while pedaling. This isn't true while coasting. As soon as you move the bars or lean sideways, you're setting yourself up for a fall.
Coasting over ice patches instead of pedaling is safer. You have more motion control when you coast over an ice patch than when you're forced to pedal. If you brake over an ice patch, you're just as bad-off.