OP YADNBU. It's the hypocracy (oh fuck I know that's wrong CBA to google) that gets me.
Any time that there is a discussion about food, of the 'I can't afford vegetables so I have to feed my children on frozen pizza' variety, anyone that suggests that seasonal vegetables and pulses are cheap and healthy gets shouted down with cries of 'but what if they don't have a supermarket, pan, knife that they can use, or what if their electric has run out, or what if they are depressed, etc etc etc etc.
There are always armies of posters that come up with reasons why it might not be easy to cook from scratch and how it is much more expensive than Iceland pizza and chips which it isn't.
But people who can't manage to cook from scratch because they haven't had chance to learn or have SNs are likely to be the exact same people that don't have perfect SPaG and if they did come on here asking for help with feeding their children with something other than Iceland pizza, they might not write their post in perfect degree level English and they would get snippy comments on their written English and if they were a new poster they would probably think 'well fuck it you bitches, I know where I'm not wanted' and not post again.
Anyone that is mentally fragile would probably get quite upset about it all.
I like that the standard of posting on Mumsnet is usually very good, mostly because I'm and old luddite that can't read txtspk, but I think that pulling up other posters on often minor errors in spelling or use of their/there/they're etc is inappropriate and incredibly rude.
English is a comparitively (sp!) complex language. I am very impressed with those with a reasonable grasp of it. Yes, the other thing, as well as education issues, English is not the first, or even second, lanuguage of everyone on here.