And in doing so, he specifically brought up Simon having killed “all those men, those boys, in that settlement so long ago.”
During Negan’s first board meeting following his return to the Sanctuary, he put Simon in the hot seat for consistently disobeying requests to not murder everyone.
This was an easy reference to the massacre brought up in the Season 7 episode “Swear,” where Oceanside’s Natania and Beatrice told Tara about the community’s bloody past, and for most viewers, it was just blindly assumed that Negan was the one responsible for all those deaths, even though that episode only referred to “the Saviors” without directly referencing Negan by name.