There's an apocryphal story about monkeys - based loosely on a real experiment - that goes something like this:
Stage 1. Monkeys 1, 2, 3, 4, and 5 live in a cage. A researcher hangs a banana down from the top and places a ladder underneath the banana. However, every time a monkey tries to climb the ladder to get to the banana, the researcher sprays the monkey with freezing cold water, causing him to retreat. The researcher ALSO sprays the other four monkeys. Pretty soon, all of the monkeys learn that none of them should go anywhere near the banana because they will all be sprayed with ice water. If an individual stubbornly tries to get the banana anyway, the other monkeys will vigorously intervene (i.e., beat him up). The monkeys not only have been conditioned into a state of learned helplessness but now actively engage in behaviors that reinforce that state.
Stage 2. Take Monkey 1 out and introduce a new monkey, Monkey A, instead. Monkey A, of course, never has been sprayed with cold water and just sees a tasty banana within reasonable reach. Every time he moves toward the banana, however, the other four monkeys start beating him up. Monkey A has no idea why this happens, but pretty soon he too internalizes the idea that no one should try and get the banana.
Stage 3. Take Monkey 2 out and introduce a new monkey, Monkey B, instead. Monkey B experiences the same thing that Monkey A did: move toward the banana and the other four monkeys start beating you up. Monkey A joins in the enforcement even though he doesn't know about and never experienced the original reason that led to the behavior.
Stage 4. Keep taking the original monkeys out until you have all new monkeys, Monkeys A through E, in the cage. By this time, the original reason for staying away from the banana has long been relegated to the dustbin of history and none of the current monkeys have experienced an icy spraying. Yet, all of the new monkeys vigorously enforce the prohibition against trying to get the banana because, hey, that's how we do things around here.