I won't labour this because I made my point before. However, the point you are missing here is that firstly doing 85mph IS illegal, safe or not and no amount of self-justification or sophistry changes that.busy shopping street at 2 in the afternoon, and doing 30mph, is
Secondly, you seem to think that a 30mph speed limit means you have the right to drive at 30mph. It does not, it simply means that 30mph is the maximum you can drive at legally.
If 30mph is too fast under a given circumstance, the law expects you to drive at a safe speed for those circumstances. If you do not and cause an accident, the charge will be driving without due care or dangerous driving even if you were only doing 20mph.
It is difficult to frame a law that takes everyone's opinion, capability and machinery into account. Therefore we get one law for all.