OK, I think this has probably already been said, but YABVU, cos in the long run, your child is not going to be able to survive on home-cooked additive- and preservative-free food forever. There's a real world out there! OF course fresh home-cooked food is best, but FGS, some pre-made stuff here and there will make no difference at all! In fact, if you keep him away from anything processed his whole life, one day he will crack and go completely overboard. I wasn't allowed sweets or biscuits at home as a child, and now I have an eating disorder because I never learned how to eat treats in moderation. And even then, I was allowed to eat them at parties etc. What do you plan to do when your DS starts mixing with other children and going to parties etc?
Secondly, you've been rather insulting to the rest of us who live in the real world, assuming that if we don't feed our children food which is cooked completely from scratch for every meal, we must be feeding them McDonalds. There are things in tins, bottles and packets which are really not that unhealthy, and which make our lives a little easier, so that we have more time to spend with our children and are less stressed out when we do so. It's all about balance.
I'm sure your nanny, like the rest of us, thought that the pasta was a pretty healthy and not unreasonable option to give your son unstead of making something from scratch. Have you bothered to ask her why? Perhaps she was running late for a toddler group or something? Sticking to a schedule with children is really quite hard and sometimes you just need to take a shortcut to get things done.