It must be resolved or managed appropriately. Must be, because unhealthy conflict directly impacts productivity, efficiency and profits. If in doubt about the negative power of this type conflict, ask some CEO friends. Take a poll in your company. See how many know there's a problem and compare the numbers to those unaware.
Chances are, most employees know something is amiss and, whenever it is, their work is impacted.
What's compelling and undeniable about tolerated personnel conflict is tracking a day in the life of a manager. Kids hit the playground for exercise and socializing only to be stopped short by adversarial bantering and threats between groups of kids. The playground supervisor had to redirect his or her focus from the welfare of the whole to the welfare of a few. Neither group reaches the desired outcome of productive exercise. The playground manager does nothing but keep people separated.