Re: Bending bones!
I would bet that when O'Sensei grabbed with his 'grip of doom' he was establishing such a deep connection between his center and his partner's center that his partner was really stuck. That is a very different feeling from trying to squeeze the stuffing out of somebody's wrist. In the second case the result is much localized pain but no control over center.
When I am teaching a brand new person who grabs like that I tell them that the pain they are causing is counterproductive, because, as Kevin said earlier in this thread, they leave themselves open to all sorts of mischief. Also, beginners who grab like that tend to bend forward and watch my wrist - they are so focused on the grab that they forget about the rest of me. Unwise.
Anyway, tell the guy to lighten up if he's doing you harm. I'm not shy about that - I need my body to keep working right so that I can keep training, and keep working (I build custom furniture and I really need my hands and arms undamaged!). Also, if you can change your timing so that you are moving just before he clamps down, then he won't be able to as well. That should also serve to show him that there is more to aikido than a very static practice.