Walt Disney did eventually warm up to unions.

The claim that Walt Disney eventually warmed up to unions can be broken down into two main components: first, his initial stance toward unions, and second, whether he later accepted or worked with them. Evidence shows that Walt Disney was initially very hostile to unionization efforts at his studio, as reflected in the 1941 Disney animators' strike where he fired many striking animators and resisted union demands.

However, after a five-week strike and considerable pressure, Disney ultimately signed a contract recognizing the Screen Cartoonist's Guild, effectively accepting union representation at his studio. This indicates a shift from outright opposition to reluctant acceptance. While Disney's initial reaction was adversarial, the eventual signing of a union contract demonstrates that he did indeed 'warm up' or at least concede to unions in practice.

This nuanced progression is well documented in multiple sources including Wikipedia's article on the Disney animators' strike and other historical accounts.thedisneyclassics.comthedisneyclassics.comWalt Disney - During the Wars & Strikes Later decades also show ongoing collaboration between Disney entities and unions, though this is beyond Walt Disney's personal involvement due to his death in 1966.