I dont't think a single child tends to turn out spoilt. Whether a kid turns out spoilt or not depends on the upbringing of the child. Children who have siblings can also be spoilt if proper discipline and teaching is not instilled at home.
My hubby and I wnated to have only one child. But when we look at our son play on his own, we feel that he really looks lonely and would like to give him a sibling. This doesn't mean that the 2nd child is not impt or is a convenient choice. If we choose to have another child, we would definitely love him/her the same as our first.
As for dealing with feedback, we do selective listening. Whatever is constructive we accept. Whatever is not, we just nod and brush it off after.