That comparison can certainly be made and a lot of people don't buy Apple products. Nothing flame worthy about that. Apple has as big enough market share they are not interested in making their ecosystem open. In my opinion, Garmin on the other hand, should be a little more worried about competition. The rise of tablet apps and iFly has eaten their lunch in the handheld/portable area. Dynon, Avidyne etc seem to be more open, quite popular and appear to be growing.
Garmin doesn't have to "support" iFly, all they need to do is publish their protocol or at least share with partners.