Not to acuse anyone particular, but a perrenial problem of the internet appears to be the anonymity of posting online. Given this is 'mumsnet', one would hope all posters are indeed female, genuine mums, and here for proper discussion on parenting/school etc. Cases where men openly come on as men/fathers is another point for debate but at least some are honest about it.
In practice I guess its not that simple. A similar discussion site to here I once tried basically appeared to be taken over by men posing as horny women, feeding fantasies about sex, creating stories not possible in real life, even paedophilia in some cases, and the site was reported to IWF and nearly shut down. Not to suggest that is happening on MN, but is there any way of telling people posting are really who they say they are? 