Unexplained hardness won't be productive. Being difficult for no reason other than being difficult is not good. It must be accompanied with incentives, learning, education, and a clear cut message about what we expect.
If someone whipped their kid and did not tell him why, or without trying to do any find outs or teaching, then the whole learning process is out the door.
If we want long term better results, we have to mix our hardness with something, and be clear and consistent about it.