This doesn’t exist online, where it’s acceptable to post “drive by” snarky putdowns that add nothing to the conversation and don’t actually address the issue at hand - in this case, the difficulty of sourcing ingredients.
A constructive comment would have asked about the difficulty of sourcing obscure ingredients and how the founder deals with that.
Again; you are missing the point. It has nothing to do with whether the food is “authentic” or not, which is itself a highly debatable question. It has everything to do with the way you communicate to people when disagreeing with them or criticizing their ideas.
If you don’t care that people will immediately think you’re a pedantic, difficult person, as long as you get to be “right”, then sure, feel free to disregard what I wrote.
The guy said two sentences. You may think it's rude but it's probably the language barrier and he's just trying to give his honest perspective and there was no rudeness intended.
Authenticity, in other words, is not an absolute. It's a spectrum, and you can get pretty darn close to the "authentic" end of said spectrum without needing to literally import foreign water.
Or your friend interrupts a restaurant owner - a restaurant they've never eaten at - and says "you call that 'authentic' food? I doubt it."