Disney's use of racist and anti-Semitic words in private conversations was pretty normal for the time. You're probably too young to know that the word "pickaninny" has only been banned for a few decades. And the stronger phrase you mentioned would be scandalous but still used only in private conversations as a kind of joke. Many people who would make that kind of joke would never address or refer to an African-American with that word. These distinctions seem trivial and a form of gaslighting by modern standards. But since you have acknowledged that people should only be judged by the standards of their time, that fact is relevant here.

The only recorded cases I know of Disney making Anti-Semitic comments is when he discovered that some of his best animators quit to work for Warner Brothers and MGM. This was common back then. If you got mad at somebody you hurled every insult at them you could find, including ethnic and racial slurs. That was wrong, but again it was the way most people behaved back then.

Attending a rally doesn't make one a Nazi. I'm reasonably sure that he attended those rallies because he wanted to learn something about the Nazi's use of pageant and spectacle. I grew up watching the first Mickie Mouse Club, and saw the title sequence several thousand times. I was really struck when I saw "Triumph of the Will" To see how much of the imagery from that film is present in that title sequence. I think that is why he invited Leni Riefenstahl to his studio: Because he admired her as a film maker. That doesn't imply that he agreed with her politics (or more accurately her willingness to be complicit with an unspeakable evil, whether she agreed with it or not.)