My child has travelled thousands of miles in Club/Upper Class since he was three months old.
I have paid thousands for his seat.
he has as much right to fly there as you do, or perhaps even more as we actually pay from our own pocket
(I am nor going into behaviour, as it is a given that my child is well behaved, more so than some of the arrogant seats paid by their company buisness men I have witnessed in Club!)