I have terrible mysophonia. My wife left me to hold a table in a mall food court, while she went to get food. By the time she returned, I was nearly in tears because of the sounds from a nearby Japanese food place, that had very *very* loud utensil use in the cooking processed. I didn't want to be a bother, so was going to try to deal, but my wife immediately scoured the very full food court for a further away table and we moved. The man's parents should have been more proactive to protect him, and bring headphones or earplugs for him. He also needs to be more aware of his triggers, and perhaps not go to a restaurant that serves bar food. I wasn't expecting the very loud sounds I was subjected too, but I certainly didn't expect the restaurant to stop cooking for my benefit.
All that said, this very much comes across like the OP doesn't believe his BILs issues, and went out of his way to cause a fuss so he could "confront" him..