The strongest force that perpetuates horizontal hostility is denial by both the nurses who are committing the hostile behaviors and the targets who are keeping silent. When any behavior has been a part of a culture for a very long time, it is perceived as normal.
Witnesses also play a role in perpetuating horizontal hostility. For example, senior nurses witness overt behaviors intended to diminish new nurses on the unit; what they see matches their own orientation, so they don't identify the behavior as a problem.
-Kathleen Bartholomew, RN, MN