I'm not saying Frazier should have done anything differently. What I am saying is that after the fact Frazier would have legitimate grounds to be concerned with potential criticism that he should have been suspicious about Oswald's activities. Thus, his story becomes that he didn't pay much attention to the long bag, didn't discuss the presidential visit with Oswald on the drive to work even though it was the top news story of the day and Frazier was obviously interested given his presence on the street, his estimate of the bag's length might also be influenced by a desire to minimize the possibility that he should have known that it contained a rifle - so it becomes shorter than it actually was. The point being that Frazier's interests after the fact lie in the direction of minimizing the possibility that he should have known something was up. Maybe he was dumb as a brick and they didn't discuss the JFK visit etc. But if they had, I doubt Frazier would be forthcoming about it.
So, you're basically just accusing Frazier of obstruction of the investigation by obfuscating the facts as well as outright lying and then continuing to lie for the rest of his life... Got it.
You wouldn't just be speculating to fit the "facts" into your preferred narrative, would you now?
Wait, I just realized who I am talking to.... forget I asked!