The groom should have leaned into the priests ear and said something like "I'm paying the photographers much like I'm paying you, please continue. And..if you do walk out, I'll sue your ass off, now, please get back to marrying us..."
I'd be this groom, my fiancé and I are planning our wedding right now, and good photos are priority 1. We are also ensuring that our contracts have substantial penalty clauses in case one of our service providers, yes service providers
decides to get uppity at some point.
I work in a business where I'm dealing with contracts, and unfortunately breach of contract on a daily basis, I sincerely hope our wedding goes smoothly, but sometimes having a stiff financial penalty looming can prevent issues from arising in the first place. We are being fair, and ensuring that contracts protect our service providers in case we do something outlandish.
In my opinion of the youtube video, it was not a meltdown, but it was extremely unprofessional, and showed that the officiant felt he was the most important person in the room. He put the couple in a bad situation, and it showed. I would be asking him for a full refund if I were the couple.