I think, if this was my father I'd ask him what the withdrawal slip said when he got the money out, in other words - was the right account number on it? If the wrong account number was on it and my father missed it then it would have been on him. If the slip had the correct account number and the bank still moved it from the wrong account then I'd say my father was correct in his assessment of the situation. Now - I know not all banks give a withdrawal slip when getting $$$ out, ours does if I ask or if I'm doing a combo of things.
Next I'd set it up so he can do it electronically - and if he didn't like that at least get it set up and he can walk into the bank branch and sit in a office and have a bank officer do the transfer for him. Or he can call them and do it over the phone. That way he's not walking around - even if for just a short time - with so much cash on him so often.
I'll just say this, my folks are in their mid-70's and of sound mind & physically health. But my Mom is quick to perceive that someone isn't taking her seriously/treating her fairly/doing right by her and -honestly - she's wrong about it a fair bit. I've had to tell her more than once that no, the cashier at Publix did not get up that morning intending to put your milk in the same bag as your bottle of windex and they probably just weren't thinking about it, and it isn't a slight against her!
Why yes, yes I DID just spend a week visiting my parents - can you tell?!?!?!?