Re: Regrading grabs in Aikido...
I would never say that something does not happen for real - since the most determining trait of what is real is that REAL can consist of ANYTHING.
However, I am 100% in line with Josh here. I do not see the "attacks" of Aikido as the beginning of self-defense scenarios. I would think one is doing him/herself a great disservice by understanding their training in this way. I think it is much better to see the "attacks" of basic Kihon Waza training as energy prints -- prints that can be used to both measure and analyze force.
In my opinion, this gives one not only much more eventual chance of developing practical self-defense skills, this also gives one a deeper insight into the art. For example, using an energy print to analyze force, if you take mune-tsuki, it is very open to the criticism of "no one punches like that," but if you understand it as an energy print, you can see that it is the purist of all the possible manifestations capable of generating a thrusting force. If you see mune-tsuki as a punch, you are learning only how to deal against that punch - which is indeed not often manifested in the street and is a punch that is not showing great signs of skill regarding punching. However, if you see it as an energy print, as a thrusting force, you will see that you can learn a lot more about an even greater amount of things by practicing against something that "no one would ever do."
For me, when we train in any of the Katadori, we are looking to focus in on using an energy print to measure force. In particular, in much of Aikido Kihon Waza, it is very important for both Body Fusion and Directional Harmony to be present among the homolateral shoulder and the hip (with the elbow also often becoming a third element to this relationship). Techniques that cannot maintain these two concepts are very prone to failure. This Body Fusion and Directional Harmony, of course, has to be done with the predetermined sources of power (e.g. ground path, relaxation, using the muscles along the underside/back of the body, etc.) that Aikido holds in value. In other words, you can't "muscle" this. As one is learning how to do this, the real weak point that one can use to both measure his/her skill, and thereby to better calibrate themselves, is the shoulder. Two things tend to happen in the beginner when they are developing this skill and when the shoulder is being used as a measuring point (like in Katadori): 1) The shoulder gives away its relationship with the hip (and/or elbow) -- losing Body Fusion and Directional Harmony; and/or 2) the student attempts to wrongly muscle the shoulder into "maintaining" its relationship with the hip (and/or elbow). This is important information to obtain because you can't fix the problem if you don't know about it.
When this is done from the rear, as in Ushiro Ryokata-dori, one is still measuring for such things but now from a different angle -- which is important to do since single angles tend to produce bracing energies in the student (which one wants to avoid). If one is doing their Ushiro Waza more dynamically, one can actually measure for the correct holding and placement of the shoulder against many angles when practicing Ushiro Ryokata-dori. Additionally, Ushiro Waza, when it is looked at as an energy print, is vital in learning how to go from the inside to the outside of an attack and/or how to stay in the "sweet spot" on the inside of the attack using tenkan and tenkan-like maneuvers. This skill, in my opinion, is vital to the overall balance of one's art and even to its practical applications, and it is a skill that is far from being only applicable against "attacks" from the rear. For, while you should be learning how not to be attacked from the rear, and while you should be learning how to deal with that if you are, you are going to want to know how to move from the inside to the outside of an attack or how to stay in the "sweet spot" on the inside of an attack when it is coming at you from the front via tenkan and tenkan-like maneuvers (i.e. maneuvers that have you turning the opposite direction of the incoming energy). This skill is necessary in my opinion, and there is no better way of developing it than through Ushiro Waza training.
My advice is to tell your dad you are not learning about a single self-defense situation, that rather you are learning about the motion that underlies all self-defense situations (and a whole lot more).