I'm 100% convinced there was a first draft of this episode where Trixie was not a stage magician but a beast tamer or pest control, then someone from Hasbro's marketing told the writers beast taming is a taboo subject that might affect doll sales, and changes were made to the script without updating the parts of the story dependent on beast taming. The weird story about a stage pony who is far more concerned with bragging about pummeling big blue bears than she is stage tricks makes a lot more sense that way.
Back when I was younger and more passionate and argumentative, I was a vehement Trixie accuser. Basically, whatever the Trixie apologists were for, I was against. Nowadays thou, I feel Trixie was kind of a jerk for responding to criticism with aggression and confrontation, but I also feel really bad for her white lie exploding into what it became. Still have no idea how no stopping a ura major/minor ruins a magician's career. That'd be like failing to stop a forest fire ruining a painter's career.