Cartoons, like all media, are a reflection of the time in which they were created. Which is why we can look back and laugh at the future envisioned by “The Jetsons” or boggle at Donald Duck starring in a WWII propaganda movie.
It's also why we cringe when re-watching “Dumbo” and see the clear racial stereotyping of the crows, or why we wonder how the world ever thought “What Makes The Red Man Red?” song in “Peter Pan” was a good idea. So when Amazon Prime put this disclaimer up in front of “Tom & Jerry” on their instant stream, it seemed reasonable.
“Tom & Jerry” shorts may depict some ethnic and racial prejudices that were once commonplace in American society. Such depictions were wrong then and are wrong today. While not representing the Warner Bros. view of today's society, these shorts are being presented as they were originally created, because to do otherwise would be the same as claiming these prejudices never existed.
But no. Pointing out obvious racism in cartoons created 75 years ago, is apparently censorship of the highest order and the Internet went accordingly berserk.
There were those who didn't think it was necessary because children don't understand racism.
And those that didn't bother to understand what the disclaimer was actually disclaiming. (Facts are for suckers!)
Of course there were the “clever” folks saying they thought “Tom and Jerry” were animals! And clearly anthropomorphized animals could never be racist.
There were a lot of people who think acknowledging problematic elements of a classic piece of media means you can't still enjoy it. The underlying message here is “I LIKE THIS SHOW AND YOU'RE CALLING ME A RACIST!? I HATE YOU AND DON'T UNDERSTAND CRITICAL THINKING!”
And of course…the racists.
In case you want to know more about the history of racial insensitivity in old cartoons, Whoopi Goldberg gave a great explanation. This disclaimer was included as the intro to a DVD collection of “Tom & Jerry.”