But seriously, it doesn't indicate what they first got mad over. The woman off camera at the start says something about how there's kids so they should stop swearing so much so they were angry about something before the video starts. Then they just start yelling about the misgendering.
I think the employee was actually talking to the fat dude at the counter when he said "sir" but she just assumed everything was about her.
At least that black dude that smashed up the other GameStop* a few weeks ago you could hear it was about Fallout 76 and a refund/trade-in or something.
There should be a subreddit of nothing but videos of People Mad In GameStops.
*in revolutionary action.