If your teenager, for no good reason, ran your car into a tree, would you then accept that the driver is responsible for their actions?
To drive a forklift into a column is a complete lack of responsibility. Your drivers are driving machines that weigh tons. These are giant weapons. The drivers need to be accountable for their actions. I would allow one such mishap (with retraining to follow).
A repeat incident would have the driver owning a different type of job. This isn't "bumper cars".