In my head I made many cutting remarks. But the reality of this level of cognitive decline is like 90% miserably depressing and only like 10% infuriating. Plus he wouldn't be capable of understanding the criticism anyway.
I don't know what it says about you if you do it deliberately but I think there's a lot to say for asking the question anyways because his speech filters don't work properly and he might not be able to censor himself.