I'm not talking about tolerance and acceptance, of course Disney should be welcoming to everyone.
I'm just making a point on the numbers. Even in a hypothetical perfect progressive utopia where everyone is 100% accepting of everyone else, the vast majority of people (and an even higher percentage of prepubescent children) will still sort themselves into the traditional gender binary. Most people identify as men and women, boys and girls.
Analogy... You're hosting a wedding with 100 guests. Two of them are vegetarians and the rest of them want steak. The "backwards" thing to do would be to only serve beef and force the vegetarians to either eat it or go hungry. The inclusive thing to do would be to offer a vegetarian option, but still serve beef to the people who want it. Disney has chosen to take the steak off the menu entirely, serve the vegetarian meal to everyone, and strongly imply that anyone unhappy with the elimination of the meat option is a bigot.