Present them facts about the gaps in quality and reporting. A good start would be with Byron Allen’s Weather Group, Entertainment Studios Networks (ESN) and CF Entertainment — which have sued Nielsen previously over quality issues and an outdated business model.
Inform them on the specifics of what you know and not just an emotional “Nielsen su-ks” approach. Present documents if you have them. Give them specific details on what Nielsen fails to disclose, and see if they pursue things any further. Do the same by talking with Nielsen’s competitors.
The more we talk the more we disrupt, and the closer we get to a client or clients making some major noise in regards to Nielsen.