It all comes down to context: older cartoons, movies, books, etc. are all excellent ways of examining how ethnicity, religion, sexual orientation, etc. were viewed by “mainstream” society at a given time. Some of the best insights to “popular” thought at any given time during the last 200 years or so is to look at political cartoons: they generally sum up whatever conflict (political or military) is all about, in the broadest terms.
However, putting the example into some kind of wider context is important: making judgement on the past from one particular source (movie, television show, book, or whatever) can be highly misleading. Every author, artist, or writer brings their own values to bear, consciously or otherwise, when creating something. A cartoon about Jews from Der Sturmer (the official organ of the Nazi Brownshirts), for example, would represent one extreme fringe viewpoint, while a cartoon from a US or British newspaper of the time would most likely be more “mainstream.”
If older texts, scripts, etc. use language or portrayals that are now considered “racist,” or otherwise “inappropriate” they should not be censored or edited, but rather used–carefully, and in context–to illustrate the mores of the time they were produced, and to provoke discussion about how stereotypes are created and perpetuated. Censorship teaches nothing–using the Nazi film “The Eternal Jew,” for example, to show how a government uses propaganda to indoctrinate the general population with anti-religious or anti-ethnic bias (an extreme case, admittedly), is far more valuable than banning the film or cutting out those parts which are now objectionable (which would not leave much of the film!). But-- and this is important-- the audience would need to be prepared for the film, have its historic period explained, and be given some historic framework in order for the full meaning of the film to be placed in context. To show it without some kind of comment or context guide to a general audience would most likely be inappropriate.
I’m dead against the censorship of historical documents of any nature: any tampering with the content will destroy their historical value. Once you begin “adjusting” the past, you have altered the context of that document totally. Either show it uncut, or not at all. You need to educate the audience about the historic background of what they are seeing, and what the larger historical trends were that surround that particular movie, cartoon, book, etc. It is far more healthy, to face up to how minorities (of whatever type) were portrayed in history than to put on a happy face and sweep things under the carpet: on the contrary–shine as bright a light as possible on them, and take a good, hard look.
For example:
I have a display running currently dealing with the WWII homefront here in British Columbia. One of the artifacts on display is an official House Of Commons speech by a local Member of Parliament, entitled “JAPS MUST GO!” This piece deals with the anti-oriental movement here on the west coast during WWII. Even though the word “Jap” is now considered offensive, if I were to change the title of the speech, or pretend that the word “Jap” was not in daily use during the period in question, I would be grossly misrepresenting the state of affairs historically. I have balanced the use of this speech with quotes from the Canadian Prime Minister of the day saying that at no time did he consider Japanese-Canadians a threat (although he still interned them!)