How's a progressive parent to resond?
'Life's not fair' - nah, that's a bit undermining and depressing, politically speaking. Let's not go there.
'I'm sorry you feel that way' - while it may be how the book-writing-pop-psychologist experts would like me to respond.... Meh.
'Shh! Don't let the overlords hear you say that! If you manage to get to the age of 18 complaining about unfairness everytime you don't get exactly what you *want* when you have everything you *need*, I will be deemed a failure as a momster and have no choice but to eat you for dinner. I'm trying to watch my weight and you'l totally throw that off and THAT is not fair!'
Heh... Little bugger ran off before I could finish my evil monologue. Foo.