Honest answer?
You're up against too many vested interests and it's too easy for politicians to put up the "we're doing this for safety reasons" argument. No amount of shouting is going to make a difference.
You've just got to let them run their course and be proved wrong over time - probably be 5-10 years before cameras will take a downturn. It's a big gravy train and it's going to take a long time to turn it around.
Basically it needs to get to the point where a
huge number of drivers have been caught by them and feel that it was unjustified. The numbers have to be massive and get to a tipping point.
For example, there are about 23 million drivers in the UK (population circa 65 million.) In the last 10 years over 12 million drivers have had speeding fines and penalty points from cameras -
that's more than half the driving population! and we're not at the tipping point yet. Some see it's getting close but there are too many vested interest keeping it going, not to mention over $300 million income a year for the UK treasury.
In the meantime perhaps the NMA and NRA can join forces?