95% of all speed enforcement is for revenue raising purposes only. Not for reckless driving. Not for being dangerous to other motorists. There's one town in Ohio that has something like 500 feet of Interstate highway within its borders. They don't even have an on or off-ramp. They vigorously "enforce" the speed limit to such an extent that the Ohio legistlature passed a law that (I forget) either requires an interchange or a mile of interstate or something before a town/community can pull people over.
Theoretically, I agree with your statement of princciple.
Practically, when *everyone* breaks the law, the law is bad. And *everyone* breaks speed limit laws - in fact, if you don't break the law, you very likely are endangering yourself and other drivers by driving so much slower than the prevailing traffic.