What 'evidence' are you being forced to accept? As I have previously stated you have a license to drive to the laws of the road, not to change them to what you think they should be.
I pointed out in my first post in this thread there are other factors that need to be taken into account when setting speed limits, in that case the fact that the road has animals roaming across it, that drivers do not take into account on individual journeys. The speed limit has been lowered and there has been a measured improvement in safety on that road.
There is merit in having variable speed limits. Indeed if you read the article, one of the suggestions is to have temporary 20mph limits around schools at start and finish times (which already happens in Scotland). In general variable limits involves temporarily lowering the limit to improve traffic flow such as on the M42 and M25 as a car at 70mph needs significantly more road space than the same car at 50mph.
By the way speed cameras are sighted where amongst others the following criteria are met: -
At least 4 KSI per km in last three calendar years (not per annum)
At least 8 PIA per km in last three calendar years
Causation factors indicate that speeding was a contributory factor in some or all of the accidents – sites that are clearly not speed-related have been de-selected
(full list of criteria can be found
here)