I think we have to make a distinction between legally entitled to do something and whether they should do something. Based on current copyright laws, the copywriter holders are absolutely entitled to change the work. As the owners of art, they shouldn't change it from what the artist did. If I owned the Mona Lisa, I would be able to draw a mustache on her but it would be disrespectful to Di Vinci and all his fans.

>he did make changes to the Oompa-Loompas

The key idea here is he made changes, which is his prerogative as the author. He had a problem with someone else changing his words. This leads me to believe that he would be appalled at what the publisher did but might have agreed to make changes if they were presented to him.

The big problem isn't the change (although the reasoning is stupid) it the fact that you don't get to change the author's words and pretend it is still written by the author. Some of the changes completely change the imagery in the book and we can't know if Dahl would been ok with changing those images.