I've spent the morning trying to do something positive, so I've contacted companies who have deals going with MN to say that I'll support them as long as they support MN.
Along the lines of:
"Good to see your tie-in with the popular website MUMSNET. I'll buy your products as long as you support Mumsnet which in turn supports hundreds of thousands of women - you know, the ones with all that spending power. Mumsnet is a place where women can talk about the things that affect them, and discuss products, lifestyles, children, medical issues. The site has millions of hits a week.
Please don't let a vocal but actually quite small group of radical activists upset the equilibrium with their unpleasant and inaccurate portrayals of the women on Mumsnet.
Thank you."
I think if lots of MNers did this kind of thing and gave this kind of feedback it would be a positive step.
I used the companies' online contact pages. I just googled 'contact + company name'.