If you were upgraded ahead of time, and you knew you had dietary restrictions, why did you not change your seat assignment so that you would be sure to have a choice?
It strikes me that UA flyers believe the airline should be mindreader as to your wants and/or needs. Then if you don't get your way you whine about it. Yes, CO flyers can be whiners too, but I can't remember seeing so many petty post from CO ff'ers.