I agree with you, his comments were totally arrogant and uninformed. He seems to assume that of course he will be fit and well until he is very old, that of course you can only do worthwhile things while fit and well, that of course these 'worthwhile' things must be of a certain kind...
So I'd like to know what he would have done if he had become ill at 21? Got into bed and waited to die? If he had raised a child with severe disabilities? Given up? Said, well, I won't actually kill the child but we'll refuse further treatment because his life is not worth living.
I'll give the benefit of the doubt that he wouldn't - he'd have learned how to struggle to do what you can, to create meaning in the face of adversity. He would have fought for his child to have opportunities and to be valued as a human life even if none of those opportunities could be taken. He'd have had to face the fact that he, his family, anyone, can become ill or disabled at any time. He is not immune or special.
So yes, he is talking crap basically. Love your blog post.