If this is the case, why do these incidents keep happening?
I guess it comes back to the cliched "All that is necessary for the triumph of evil is that good [people] do nothing".
And having a stated policy in place is a pro-active way to demonstrate "Hey, in case you were wondering, this kind of behaviour's not okay and this is how we'll deal with it".
Because as a culture we don't know how to talk about these things - when they happen and when we see and hear about them. And when TV shows - like Freaks and Geeks - come along and try, they're canceled after one season.