If you accept someones right to do something you don't write a letter to a national newspaper moaning about how awful that choice made you feel.
I think it's entirely possible to express your feelings, anonymously, about a person's decision while still knowing they had the right to make that decision. And I don't think there's anything wrong in doing it anonymously, with no identifying details.
But then I believe that all humans are a complicated mess of conflicting emotions and capable of feeling more than one thing at a time.
That column exists to spark emotion and debate, which is clearly what has happened here. There are some absolute twats in that column sometimes; seems you don't have to be a nice person to be thought provoking.