Before section 230, there had been a couple of court cases. One held that a particular provider was not liable for anything posted on it, because it did not do any filtering or blocking at all. Another held that a different provider was liable for what users posted, because it did do some filtering and blocking.

Congress felt these outcomes were wrong, and section 230 was specifically meant to make providers not liable for user provided content, regardless of whether or not they did any filtering or blocking.