Has he ever seriously worried about publicity? Besides, he wasn't slandered until the law says he was slandered. I could believe he also suffered genuine harm as a result, and I imagine at least some of the $$$ Kyle made from the book was as a result of the lies he told.
De mortuis nil nisi bonum, but elite soldier or not, this Kyle character sounds like he might have been as big a blowhard as Ventura.