In regards pension and career progression... I was already on UPS1 (Upper Pay Scale point 1 of 3, which does not have automatic progression), at a time where school funding was being cut to the bone. I could be the best teacher ever and never get promoted to UPS2, extra responsibility roles were being phased out with the roles split and put upon staff for no extra money or time, and the public sector pay freeze meant my salary was real terms reducing every year. So career progression and pay rises weren't a consideration.
Pension... Well, I'm only 34. I have a pension from my years teaching, and I'll be able to get back to work from January next year should I wish to. I've probably got another 30+ years to work, with little expectation of a state pension at all. Meanwhile we've arranged our finances so any money I make is a bonus which can go straight in to savings for paying off mortgages and topping up pensions.
So, I think it's silly to assume a woman is always screwing herself long term to be a SAHP. It's a little insulting too, the assumption that these weren't all factors taken in to account. By saying the end decision is wrong no matter what, you are alienating women and their choices.
Certainly it's wrong that women are priced out of work by childcare, but that isn't the woman who is wrong, it's society and government. Berating her for the choice she's made in the society in which she lives, rather than a fantasy utopia, is foolish.