Why should he prove his concepts are true? Everybody should do things they believe are helpoful or enjoyable for themselves. Why should we prove anything to others? If they Day comes when he needs to use those skills for survival, then they are brought to test.The best way for him to prove his concepts are righ is to put them to the test.
As Rokas did.
Other way he is no more than other aikido master who talks, talks, talks and nothing more.
I am pretty sure the possibility of being attacked with the fists on the streets is much much higher than possibility of being attacked with the knife. Better for him to learn how to protect the jaw.
BTW I do not see the difference between breaking somebodys nose in "ritual combat" and breaking somebodys nose in "real fight".
Technique and damage is the same,