Speed is a tricky subject. There is no doubt that speed kills: if a person is hit by a car travelling at 20mph, that person has a 1 in 10 chance of being killed. When that speed is doubled to 40mph, those chances are reversed - you would only have a 1 in 10 chance of surviving.
So yes, driving more slowly reduces the risk of road deaths.
However, a lack of speeding tickets is no more proof that you are a good driver than having speeding endorsements is proof that you are a bad one. Someone may drive inappropriately slowly, causing other drivers to get annoyed and do something stupid. That would not bring that person speeding tickets but it certainly wouldn't be good driving. Equally a person who drives like a nutter then brakes hard in time for cameras may also not have points on their licence but you wouldn't want them on the road.
Speed kills if you drive too fast to react to foreseeable hazards. A child running out in front of a car is often foreseeable. You may not actually be able to see the child itself but a flying ball, a school, other kids, an ice cream van, a park or just any residential street in the middle of day should all suggest that a child may be there somewhere.
To give another example, on a motorway in heavy traffic, cars often drive too close to each other to be able to stop if the car in front brakes suddenly. Say a lorry has a blow out and there is still debris on the road. One car spots the debris too late, brakes, swerves, and this action ripples back causing several cars to collide with each other at 70mph. Fair enough, none of those drivers could see that there was debris on the road - but nor could they see that there wasn't.
In both of these cases, a safe speed is actually below the speed limit. Limits and speed cameras reduce the need to think. The law on speeding and licence points gives the message that staying within the speed limit is all that is required to stay safe but it isn't. You also have to look ahead and to think. Equally, there are cases where driving above the speed limit is reasonably safe, especially as the limits are established for day time, busy driving, but unfortunately the law does not take this into account either. Driving at 40mph past a school at 3.15 in the afternoon is not the same crime as driving past the same school at 40mph at 3.15 in the morning and should not carry the same penalty but it does. Cameras and endorsements are blunt tools that give a blunt and misleading message.
But however much you may think that the use and placement of speed cameras is less about road safety and more about making councils money, if you persistently get caught driving above the speed limit thus risking your licence and thereby your lifestyle, that's your own silly fault! The signs are plenty big enough!