It doesn't really matter whether the situation is by design or simply an unintended consequence. That highway speed limits are often set below the speed at which the vast majority of drivers travel means in practice that police can stop whoever they want for any reason whatsoever. It doesn't have to be a conspiracy for it to be tyranny.
Most speed laws are based on some semblance of science. Granted there is often that extra percentage, but it doesn't kill anyone to slow down a little.
"a review of available speed studies demonstrates that the posted speed limit is almost always set well below the 85th-percentile speed by as much as 8 to 12 mph"
