Putting aside whether federal guidelines required mask-wearing in this case, Disney is a privately-owned business, and they get to make the rules about what manner of dress is allowed or prohibited in their parks (so long as they're not running afoul of existing laws, none of which apply here). They can require you to wear a shirt, shoes, Mouse ears, masks, whatever. They can also enforce their rules differently, and decide, for example, that masks must be worn the moment a child turns 2, while at the same time, you don't need to buy a ticket for a 2-year-old who happens to turn 3 during their visit.
OP, I understand that this issue was a grey area about which you sought advice ahead of time, and that you didn't go into this intending to break the rules. However, you deliberately forced the issue by announcing your daughter's age, and then got called on it. The best thing you could have done was to model appropriate grownup behavior for your daughter, by accepting the rules with grace once they were clarified for you, and following them. Unfortunately, it sounds like all you did was to throw a tantrum, and then come back later to repeat the same bad behavior again, like... well, a 2-year-old.