Like the Toronto teacher who was wearing those gigantic prosthetic breasts, this seems like one of those things that at surface level sounds unjust to the employee ("what they do outside of work is their own busoness" etc), but when you know the details it becomes clear that the employee has been doing a number of things to justify firing and has just been trying to spin a story of persecution to the media.
Nothing inherently wrong IMO with a teacher doing porn so long as those two jobs are completely compartmentalized, but that's also a very fine line, and I don't get the impression (from the admittedly incomplete info of the news articles) that this person was doing that properly and in good faith.