My answer to this is simple: we avoid the argument by admitting that we don't really know. I don't mean to dismiss scholarship, but the fact is, I'm not a scholar myself, and I don't speak Japanese. Any "research" that I did would be in English, and thus, at second-hand at best. I can look at the work of others, and I can make intelligent decisions about whose scholarship (and motives) I am inclined to trust. But even the most rigorous and impartial scholar doesn't really know, either. No one does.
To a point, that's true, but it's not really a valid argument. Understanding a historic person (or anyone, for that matter) isn't a binary, yes-no, situation, it's a continuum. And yes, I think that it is important to make the attempt, otherwise why study any history of any kind? Isn't it a forgone conclusion that studying what people thought in the past is useful to those of us living in the present and moving to the future?
I've also found, oddly enough, that many Aikido students are actually interested in what the Founder of their art had to say.