Re: Measuring if/how martial arts helps one become a better person
Well, on some level of course most any activity can be personally fulfilling and beneficial. In that respect most anything can make you a "better" person. That said, there is a general conception among *some* that martial arts are also about improving the person in many ways. Heck, as Dr. Goldsbury has already pointed out O-Sensei approached it much like a religion, which is obviously quite an extreme compared to, say, playing tennis for fun and fulfillment. Not the same thing on any level.
And of course there is all the stuff about the so-called Warrior Sage, Warrior Monk, or the enlightened guru that permeates many of these arts. Sometimes it's downplayed or not there at all. But at other times you cannot deny that there is a strong undercurrent of influence. Heck, Ueshiba's doka are great examples of exactly the sort of "enlightened" proclamations going clearly in to philosophical and religious concepts. And we've had entire discussions here of things like "katsujinken" that often go much further than just describing different ideas of proper sword strategy in to areas of moral worth and ethical action.
So all that said I think these questions are asked and answered quite differently depending on the person, style and context involved. And there is no doubt that what I may get out of my practice is most likely quite different from what everyone else gets out of it in the larger scheme of things.
But once we start drilling down and being specific about what exactly we're talking about, be it one-on-one fighting efficiency, martial effectiveness of sword use, grappling, atemi, etc. there are objective criterion by which to judge the value of those things. I.e., it works or it doesn't to use a very simplified description. Of course things get hazy when we get more nuanced, but on *those* issues there can be objective statements made that are fairly straightforward in evaluation. So a guy doing no-touch ki throws that don't work on anyone other than his or her students is probably not demonstrating something that will work on anyone *other* than those students. That said it might be fun, enlightening, enriching practice for those involved working on increasing their sensitivity and awareness (or whatever --- I'm reaching here since it's not really my bag either).
Anyway, saying studying martial arts does not guarantee becoming a good person is an obvious statement to me. That said, sometimes it is taught with that as an express, specific and important goal for that particular group. Whether it works or not... Well... Let's reference scandals in the Catholic Church, terrorist activities carried out by many religious groups, terrorist activities done by "patriots" who believe they're being oppressed, etc. That's a really big, muddy area...
Me, I just train to try to get better at the body skills I find so interesting in Aikido. And what those skills imply about body mechanics, about psychology, etc.