Fundamentally you did the right thing, and I think you can salvage that. The lesson learned was how to go about things. But ultimately if the guy refused your every intervention, and was determined to fly walking off would be the only way to prevent that. I think you should have tried a progressive escalation, including calling the company.
The way to spin it is you were new, being asked to things they just trained you not to do, unfamiliar with airline culture, and ill-equipped to handle the stereotypical "nightmare CA". Your takeaway is that you learned from it, and have matured since, and have a much better understanding of airline life and associated costs and stress.
You'll have no problem getting hired at a regional, and when the time comes you should be able to get on with a major. You'll have to address...
- What you did right (not fly).
- What you did wrong.
- What you learned, how you would do it differently.
- How you have matured since.
Make sure you keep a clean record going forward, too many hiccups constitutes a trend.