The police force of Estelline, and in particular the officer profiled in the story linked above, are basically legal muggers. Speed-trap towns like these are predatory, unfriendly, and hypocritical. I say "hypocritical" because the stated duty of the police is to stop lawbreakers, yet in order to function, they hope for more people to break the law.
The speed limit drops suddenly from 70 mph to 50 mph. This is one of the symptoms of a speed trap. Sure, they say it's clearly marked, but why don't they do like many towns along US 59 in East Texas and put up a series of speed limit signs, each reducing the speed by 5 or 10 mph? Why force motorists to suddenly drop 20 mph in one go? Because they care more about making money than safety.
If you visit Texas, keep a scrupulous eye on your speedometer. And, if possible, stick to the interstates.