The leak led to the deaths of many people, for which Assange was blamed. But he warned the State Department of the imminent leak, which was out of his control, and told them to get people out of harm's way.
Wikileaks was planning on redacting names of people who would be put in danger by the leak.
Also, Wikileaks wrote to the State Department, asking them what they wanted/needed redacted from the cables. The State Department responded with a "fuck off".