I had a flick through one of the banned books I have and I was unable to fault anything in it. I had to look up what the problem was and then check back and I felt it was a really big stretch to call it offensive.
And after all this, if one of the books did contain something truly bad, why not do something like Disney and add a disclaimer or edit the content? The material in question in these books is less than 1% and isn't core to the story or images.
As for the second question, that's a question for Dr. Seuss Enterprises; they made this decision about the works in their custody.