It's rather amazing how when you call out people's preconception they hold strongly, you'll easily get downvoted here, regardless of how well founded or supported that preconception is.

If the original comment had mentioned how the purchase was from a black vendor, or a gay vendor, people would be up in arms about what that unjustly implies, and how without any sort of data to back that it's just stereotyping (at best). Do it for China, where people already have a strong preconception of the types of vendors present, and all that rational separation of anecdote and data and needing to justify your statements goes right out the window.

This isn't to say you can't call out vendors from China if you suspect they are a problem in higher proportions than other vendors. The original comment could have included "I suspect this may be a problem exhibited more often from vendors from China, but don't have data to back that up" or more strong statements with some data, but did not. Instead we have a statement that only adds to the comment when combined with your own preconceptions, since it adds nothing to the circumstances of the described situation without your own preconceptions.