The magic isn't the Disney Princesses behaving as we all should; it is how much it meant to the Redditor who shared this video of their magical experience. While these responses were not universal to all the characters, in the comments, the poster says they were heartfelt and only deepened their love of Disney Parks.
The cast members portraying the princesses must also appreciate these interactions far more than the sexual assaults and touching they are frequently subject to. I'd guess they wish their days were filled with this princess rather than those jerks.