No one said that being a considerate person is compulsory, or that anyone has a 'right' to anything just because they have children.
People obviously have the right to focus on themselves and their own wants/needs. It's just not how I was raised. I don't only offer seats on buses and trains to disabled and elderly people, I also offer my seat to pregnant women and people with young children. It's completely irrelevant that they chose to have the children.
As I go about my life I always try to be considerate of others, irrespective of whether they have 'the right'. Low paid waiters and waitresses don't have a 'right' to a tip, but I always tip them anyway because I remember what it was like to be a low paid waitress.
And before anyone mentions anything about female socialisation, I learned this from watching my Dad, who is a complete gentleman.
If I am flying with my family I will always pay to stay together, but most of the flights I take these days are on my own. I usually opt for an aisle seat, but it really wouldn't be much skin off my nose to swap seats for a nervous 12 year old, even to a rubbish middle one.
The arseholery I referred to is from posters on this thread and the general attitude towards a nervous 12 year old.
I'd also like to add that flying frequently as an unaccompanied minor does not necessarily translate into being a good flyer when you get older. I flew on my own from the age of 10, and by 16 was taking a return shorthaul flight every weekend. I still hate flying.