Sorry… why does it matter that it was in a Disney show when you were growing up?
Again, ‘retarded’ has been an insult for a very long time. It hasn’t even been federally legal to use the term “mental retardation” since 2010 (more than “barely a decade”) and by that time, the only people using the term was the federal government. The same federal government that used ‘negro’ until the 2000s. Are you going to claim ‘negro’ was the polite way to refer to a person in 1995 next?
But sure, call it polite. People who are actually bullied by it would disagree with you.