It's not irrefutable. I have tons of quotes but people say I post them too much.
So, let me break things down just a bit.
First: tanto. It would be extremely hard to prove Ueshiba's aikido was based upon tanto usage. In fact, it's very hard to find where Ueshiba practiced with a tanto.
Second: Jo. It's also hard to prove Ueshiba's aikido was based upon "jo" usage. There is very little correlation that Ueshiba was using a "jo". For quite a few demonstrations, he used a short staff that was sharpened on one end, like a short spear and not a jo. It's also mentioned often that Ueshiba trained with a spear, not a jo. Finally, in regards to the actual usage of the jo, Ueshiba wields it with spiritual ideology driven by his aiki body, not by any martial jutsu. There is no correlation between Ueshiba's using a "jo" and any other jojutsu or jodo.
Third: Bokken/sword. There are far too many references of students having to go outside to learn how to use the sword. There are references of Ueshiba stating he didn't want weapons taught at hombu. Saito was an exception. There are references in pre-war where students had to learn on their own how to use the sword.
There are koryu that are weapons based arts. The Filipino martial arts are a weapons based art. Aikido is not. What was it Ueshiba was famous for saying when talking about sword work? He would say something like, you would do it (the sword kata/form/whatever) this way with aiki.