It was well known before Kimmel made his comments that the shooter was in a romantic relationship with a trans woman. Having said that, even if he did not know about that relationship it was irresponsible of Kimmel to repeat rumors he could not have known were true that the shooter was maga.
He did not assert they were unknown: “We hit some new lows over the weekend with the MAGA gang trying to characterize this kid who killed Charlie Kirk as anything other than one of them,” Kimmel said in his Sept. 15 monologue.
I guess that leaves the question as to why Kimmel did not say: 'We hit some new lows over the weekend when people of all political stripes were trying to characterize this kid who killed Charlie Kirk as anything other than one of them'. Because that seems like it gives more information to the viewer because that is what actually happened and acknowledging people from both sides were doing the 'bad thing' should help to bring people together instead of driving people apart.
Mr. Kimmel is making a series of jokes about how members of the party in power are reacting, including a clip of the president not seeming to care when asked about Mr. Kirk's death.