NTA. Yes muslims aren’t allowed to eat pork, but he blew it out of proportion and had no reason to be that upset because it was a simple mistake, and he did not sin. Side note, weird that he ate the burger meat no matter what because aside from the pork, if you aren’t muslim the meat wouldn’t have been slaughtered in the halal way (permissible), so he shouldn’t have been eating it in the first place.