This dude is pretty scummy though, and probably deserves it. You've got a girl struggling to get lunch, probably really hungry, and then you insult her deeply based on the fact that she's invisible.
He was basically a racist heartless jerk, he totally deserved that.
Also note that he didn't even try to help her, despite being the only one who should've helped her there since he acknowledged her presence and the fact she had difficulty ordering her food.
That accusation of him being racist is a bit of a stretch. Now heartless and a jerk, sure. But as an attitude between friends, this is closer to just casual banter.
Plus keep in mind that all of this is just a singular page. The setup is a busy lunch time, everyone's rushing to get food. These two aren't on the front of the crowd or line and neither of them are pushing too hard. She's trying to push forward though somewhat although not aggressively.
He's just bantering with her and arguably pointing out that she's not trying to voice her desires loud enough. So instead of taking his advice, she's taking it out on him by actively putting him in trouble and as I previously stated, in a real life environment, this is a life ruining event.
Her mild inconvenience for a day does not justify her doing something that could ruin his entire future. It's like if you were trying to argue that a girl is in the right for making false accusation of sexual harassment on a guy just because he called her ugly.
One hurts someone's feeling. The other destroys their entire life.
At best, what you could've argued that he might've deserved was her insulting him back directly to match that level of banter. Or if you want to go the classic anime/manga tsundere route, physical assault on him like elbowing him in the stomach or something. Which is the more typically accepted level of escalation of violence against men.