It's one of those things where some corroborating data can help rule it out. But you may be right, we can never be sure. One thing -- didn't the Sagawa dojo have similar stuff posted earlier? If so, maybe Takeda had some core message like this, which the different branches picked up from him.
I was thinking about Takeda-- he saw people do bad things-- from a lot of different angles (per Amdur's HIPS). If his known acts of public violence were indeed during events of unprovoked attack by others against him, maybe he really did develop a vision for a better world. He spent so much time teaching police-- maybe because he saw them as what they ideally are, a way to have society protected from those who make the world bad.
The fact that he had a temper means nothing to me in terms of his vision. In fact both his temper and his proposed vision for a better world may have been fostered by the same experiences of witnessing bad things.
One thing worth noting is That Sokaku stressed that daito ryu (or the inner "oshiki uchi" techniques at any event) were essentially defensive in nature and should not be used offensively. They also should be measured: the idea was to render an assailant so that they were no longer a threat Straight off, you have an ethical stance, or one that at least cultivates a certain attitude or character.