They're not talking being judged by the employees. They're talking being judged by the other shoppers.

Imagine being a foreign tourist to America, going into a middle-American Wal-Mart — one far away from places where any tourists would ever bother to visit. Some American dudebro wandering through the aisle asks you a question (in English), and then gets pissed off when they realize that you don't speak English, and starts berating you and wondering out loud what his town is coming to.

The social-anxiety expectation for the experience of shopping in a small neighbourhood ethnic grocery store, is the projected reverse of that: the shoppers there seeing you there bumbling about, unable to pronounce any of the names of the items, and responding by wondering angrily in $language what their district-of-the-town is coming to, i.e. when their nice little ethnic enclave community got so gentrified/whitewashed that "people like that" started showing up.

(Despite being white, it's the racist American dudebro part of this that I've experienced before, second-hand, while taking my (non-white) partner on a trip to show them a more-rural area I used to live in. That was an experience I don't want to repeat.)