An extreme reaction to bad events. A policy that no deviation from the rule, no matter how small, or whatever its intention, will be accepted. Often includes going after just the appearance of violating the policy, and sometimes even going after the appearance of having the appearance of violating the policy.

After some incidents of school shootings, zero tolerance has been the rule at some schools, who have done such wonderful things as suspending a girl for months because she had fingernail clippers that supposedly had a small knife in them. Or suspending a boy for four months because he convinced a suicidal girl to give him the knife and he put it inside his locker.

Zero tolerance is in effect the sacrifice of a few for the good of the others.