Legislating for quality debate
PJ2, as a one-time PPL but full-time scholar of public discourse, I absolutely understand the frustration of informed professionals like you, but no amount of 'cleansing' is going to stop this. From my experience across many media, and from my observations of PPruNe, you can't legislate for quality. Instead, IMHO, what works is the public availability of information sources that do not have a vested interest, such that competing views get fed into forums like this.
Compare this thread with the Buffalo Q400 thread, or the Hudson ditching. What characterises those threads is not that the people commenting were any less fallibly human, but that many of those fallible fellow-creatures who did leap in had instantaneous access to high quality, publicly-available tracking, ATC and other data direct from the sources. While even the Buffalo thread, nonetheless, descended at times into ill-informed nonsense about tail-stalls etc, the base level quality information was there.
Now look at things like the EK tailstrike incident at MEL. No publicly available data sources -- the only source was EK themselves and the Australian authorities, plus some quick-thinking MEL groundcrew -- and the quality there is likewise poor. The same is panning out in the AF447 case - little publicly available alternative sources of data with the notable exception of some fantastic meteo analysis. It is not surprising that the quality discussion is on the meteo facts, on which there is good, alternative-source data; the crap is based on information drip fed without alternatives by AF and the Brazilian military.
Given all that, we should either be lobbying for flight data to be publicly available worldwide; or we should give up and have some sort of professional pilots only forum. How you would get that is something I can't tell you; whether that would be a good thing, given the excellent meteo, engineering and retired pilot contributions made every day, is another matter entirely.
The short-term lesson -- if you're going to have a good quality discussion forum, pray no-one in the media finds it. Once they do, you not only attract them, you attract all the goons have made the AF447 discussion the mess it is today.