As for the subject, I've nothing particularly against hiding speed cameras. It's basically a spot check that you can't avoid. That we should have a system where with a bit of knowledge you can do what you like except in a very specific, easily discovered place is a bit odd.
But, I do have something against the principle of speed cameras, if not the practice, and certainly the heavy emphasis on speed rather than personal judgement, behaviour and responsibility. Unfortunately cameras have become necessary, but they are in part responsible for that. If you make driving all about blind compliance with a number on a stick, often an arbitrary and sometimes poorly chosen one, then you stop it being about personal decision making and the whole spectrum of other things that you probably won't be caught for. I'd rather people were channelled towards doing that through education, testing etc, but that's expensive, and so we have a lazy, authoritarian way of doing it instead.