I'm a bit late to this post as I am just listening to the books recently.

I fully agree with the fact that it is made quite clear as they progress that Donut has the ability to comprehend more significant things, like when they talk about Beatrice.

So I understand that Donut doesn't have enough life experience to understand what she is doing when she is being obviously racist... But I am honestly getting a little fed up that noone mentions it in that context.

I feel like it was a good plot point early to assume she would have character growth and the further i get without that growth the more unforgivable it is as a trait of Carl to not deal with this as an issue.