She is right that you'll face criticism sometimes about choices you make but it's really naive to think that people in real life aren't judging the choices you make. The thing that mumsnet does for me is to open my eyes to just how many people hold different views, some the same as mine which feel really supportive and some very different. This has taught me to be a bit less naive, to empathise with people more and I find that the openness and honesty is quite refreshing. It's very easy in real life to cocoon yourself in situations with people you know hold roughly the same views. I wouldn't like to be in constant conflict and there are certain threads that I'd avoid because I'd be fairly sure I'd not like what I heard. But there's nowhere like it for getting a range of actual, strongly held views.
I guess the only difference is that the views expressed against her have been very personal and pinned to an actual person rather than an anonymous mumsnet nickname/persona.