The idea he is pushing misinformation is ridiculous,he didn't speak on the motives of the shooter only on magas insistence he wasn't maga. He didn't say he was maga, merely focused on the performative finger pointing of Republicans
The only thing that could have validated such finger pointing is a belief that the shooter actually was "maga". In the absence of such a belief, to say that "maga" was disavowing the shooter is not an accusation of wrongdoing. But the claim was prefaced with an assertion that "we hit a new low" in the form of this disavowal; therefore Kimmel did see it as an accusation of wrongdoing.
Edit: and republicans definitely know the difference, but they played up a sad situation to their benefit to hurt an opponent.