The smear is not that Kyle shot looters. The smear is that he lied about shooting looters. See posts #6, #7 and #24.
This could be a hypothetical discussion between a group of snipers. . . talking about how easy it would be for snipers to get a handle the looting problem in NOLO. Put a squad of them on the Superdome roof and start taking them out. This could have been overheard and then confabulated into the story that it actually happened. . . and someone decided to give it some verisimilitude by converting it into a conversation with Chris Kyle. After all, if HE said it, it MUST be true, RIGHT? There is no guarantee that the guy quoting him is honest, is there? Or the guy quoting the guy quoting Kyle? Too far removed from Kyle. . . who cannot defend or explain what he said.