If it can be shown media outlets continued to make false claims about Kyle when the facts were available to the public and reporters, Kyle's case has merit.
I am assuming that you didn't listen to the two Barnes video clips I posted earlier in post 15 of this thread, and I don't blame you if you hadn't.
Barnes' point wasn't that a defamation case wouldn't have merit, but that it would be difficult to prove more damages to Kyle's reputation from the defamation than the state had already caused by charging him and putting him through a trial, and that a court would probably dismiss a defamation case at some point in the proceedings because of it.
He also states that Kyle's mother Wendy has a much better case, because she was never charged or tried in court, so damage to her reputation would more easily proved. (Second video clip I posted.)