G'day Triadic,
I don't see how anyone can claim discrimination for being charged a landing fee simply because they do not pay a road toll to drive to the same town. They (drivers) do however pay exhorbitant annual motor vehicle registration fees. As C of R holders do not pay an annual registration or license fee it cannot be argued that revenue for the provision and maintenance of airfields is already funded. Someone has to pay the engineers, plant operators and other staff required to maintain the airfields to a minimum acceptable standard.
As for the councils and airfield owners charging for practice approaches, well that is a blatant ripoff and they are either being poorly advised or trying to build test cases. I see on another thread Avalon are trying it on even for a GPS app / arrival.
A country shire over here tried it on a couple of years back with their NDB until it was pointed out to them that they neither owned the airspace or the navaid.