Can you kick my a**?
I have no doubt that based on what I have read and in private discussion with folks who experienced Mr Sigman Harden Threadgill and the others they have mentioned that yes they could kick mine and that's the point IMO of learning this stuff. The style of Aikido I practice emphasizes that it must be able to "handle" attacks by experienced Martial Artists and that is the only true gauge which one can measure Martial Effectiveness.
That being said my only objection to some of these discussions is the tone they take sometimes
I highly respect power which is the reason most Aikido does not work for me. Too many times when I attack most Aikidoka Aikido's fatal flaw reveals itself. most folks can't handle it outside of the practice paradigm of Uke/Nage. At least (it seems to me anyway) with Sword Based Arts ( and as Mr. Arillio has mentioned) you get used to the speed and timing of an attack. Folks who do not train with weapons in Aikido never really seem to experience the skill needed to handle opponents. Because most Aikidoka are not used to getting hit instead of entering with the intention of finishing/ending the conflict they flinch and focus on avoiding the strike or take down. Aiki is like a brick wall in my experience, and I have yet to win against a brick wall.
In a class setting I spend a great deal of time helping folks overcome the natural handicap of avoiding getting hit and have them try to understand they need to react by entering and to do all this while presenting an opening for their opponent to strike.
Let's call it the Aiki of learning how to Bull Fight. IMO Toreadors are some of the best Aikido practitioners on the planet.
If I am to follow Shoji Nishio's insistence That Aikido must be effective against other Martial Arts in order to be considered Budo then learning proper structure and Aiki is a natural expression of his philosophy.