Stay at home parents are discriminated against because the short-term government policies value parents' economic contribution through work, not their contribution to raising future generations. The gov't is happy to subsidise childcare for working parents, but stay at home parents are making a 'lifestyle choice'... When I went on mat.leave with our first, our income halved, and it wasn't that much to begin with...
We decided rather than pay x amount on childcare, that we'd make sacrifices and manage childcare between us. I work one day a week, dh works full-time, but compresses his hours to work four long days. Our personal choice, having read the research on childcare for the under 3s. Our eldest is now six, and I can see that friends children who were at nursery full-time or part-time are equally happy/secure in their attachments etc, so perhaps we were over-zealous with our ideals, but I have no regrets.
I don't expect to be paid for looking after my own children, but I do feel that the decision we took is viewed in a negative light. People might think I'm lazy, or that I'm not 'career-minded' or sufficiently driven. People feel jealous, people think we have more money than we have, people think they couldn't afford it, people think all kinds of things. Ultimately, there is more 'value' attached to working than parenting, and for that reason stay at home parents are discriminated against.
Changes to the benefits system also mean that families where one parent works have been disproportionately affected, which is unfair.
I have, for my sins, the worst of both works (which i wouldn't change, by the way!) as people treat me like I'm a Sahm when I do actually work part-time, but I work so few hours I'm not part of the team at work even though I willingly do extra. If I'm paid to work 8 hours and stay an extra four, is that not the same as a full-time worker doing an extra 20 hours? Yet it is not valued in the same way. People think I 'don't contribute' yet I have not had one day off sick through pregnancy, children being ill, or my own illness, and work v. hard... but it is 'only' one day.
I hate the way these debates polarise everything. We are all parents trying our best to make the right decisions. If people work they are doing it for their family, if people stay at home they are doing it for their family, and if they do a mixture, it's for their family. The gov't should support all families, and stop shelling out non means-tested payments to pensioners. Oh, but they are the people that vote I suppose, because we're all so busy juggling work and home and trying to make ends meet!!