George Ledyard gave an example of a guy who certainly misused his aikido power. Maybe aikido itself should never have been revealed to the public?
Maybe aikido was stripped of power to avoid examples like this one told by Ledyard being more common and causing more damage than a injured shoulder.
This way you can make it widely available while the number of the fatalities caused by powerful uncontrolled practitioneers is kept at an acceptable minimum.
Sell guns to the people, but the right to bear arms doesn't include having a fully functional Abrams tank in your lawn even if you can afford it.