The argument of its detractors is that the standard is too broad and allows nearly unlimited discretion for judges resulting in an easy rationalization for almost any result which in turn allows for personal bias to creep into their decisions.
The argument of its proponents is that not every circumstance and event can be foreseen and spelled out in statutes. As a result, Judges must have some equitable discretion to make rulings that are flexible and apply specific facts of individual cases.