The irony here is incredible. A suburban Twin Cities lib didn't know that "Uncle Tom" was racist and uses it while trying to accuse SCOTUS of racism. In fact, it's probably more racist than most people realize. Beyond the reference to the title character in "Uncle Tom's Cabin," referring to black adults as aunt and uncle is rooted in racism.
Southern whites didn't want their children to pay blacks the deference of calling them "Mr." or "Mrs." so it became tradition for white children to call them "aunt" or "uncle." (interesting how Mr. or Mrs. bothered them yet an implied familial relationship did not) It's why the "Aunt Jemima" and "Uncle Ben's" brands came under fire in recent years. Knowing their roots, I think it's time for such brands to disappear.
And if he didn't know it was racist what did he think it meant? Why did he use it?