The CTer song and dance goes like this:
1) cast doubt on the bag being found even though multiple witnesses confirm that is what happened (i.e. everyone who saw it is a liar and potential conspirator)
2) suggest it is not the bag described by Frazier (i.e. Frazier's estimate is precise with scientific accuracy)
3) then argue that even if Oswald touched it (unlucky guy that day!), it doesn't prove he carried a rifle in it or that it was his bag (the old impossible standard of proof trick in which no fact can ever be proven because no logical inference is ever allowed from the totality of circumstances).
Back on planet Earth, we know the following:
1) Oswald made an unexpected trip on the night before the assassination to the location where he kept his rifle
2) He carried a long bag to work the following morning which he confirmed to Frazier was not his lunch
3) No long bag matching Frazier's exact description was ever found in the TSBD and Oswald himself denied carrying any such long bag instead claiming he carried only his lunch (either making him or Frazier a liar)
4) The bag was found near the SN from which bullet casings from Oswald's rifle were found (on the same floor where his rifle was found)
5) Oswald's prints were on the bag and the nearby SN boxes (unlike any other TSBD employee) and rifle
6) The bag is long enough to contain the rifle found on that floor which belonged to Oswald
7) No one who worked in the TSBD has ever come forward with any explanation as to why this strange bag was on the 6th floor or suggest that it had some work-related purpose for being there or that it belonged to them. As a result, there in no explanation for the bag's presence in that location by anyone else who worked in the building. There are no apparent examples of any such similar bags in the building to suggest a work-related purpose for such a bag despite a number of photos taken on that floor and search of the building. The bag appears to be an unexplained anomaly after 50 plus years if not the bag used by Oswald to carry the rifle.