The foreign tourist might happen to be correct this one time, but "I'm a tourist who has been there" is not anything I have ever heard gives one power to be quite authoritative. Visiting one or more times is not remotely on par with "I have a PhD in the subject."

I'm not sure I'd say "one or more times" really sums up going dozens of times, as umanwizard said they have. While I'll give you that we don't know if they have a PhD (which, sure, would be more definite authority), evidently they have the means to travel extensively, which could well put them in more diverse areas than someone from Mexico would go.

I already acknowledged they may be correct. I will further formally acknowledge they may even be highly knowledgeable.

The problem is that citing "I'm a habitual tourist" is not really a credential anyone can verify. Maybe "I'm a travel blogger as well and here is a link to my 10 year long blog and here are the posts about the many times I went to this place, so you can check the depth of my knowledge if you desire." would work.

The phrase quite authoritative suggests credentialing. I am extremely knowledgeable about a number of subjects. I even have 6 years of college. But I have a serious problem with trying to get taken seriously in part because a lot of my credentials are akin to "I'm a habitual tourist."

Maybe you really are a habitual tourist. Maybe you are more knowledgeable on the subject than the world's foremost expert with two PhDs. The problem is that "I'm a habitual tourist" simply fails as a verifiable credential as a stand alone thing without something to back up your claim of depth of accurate knowledge.

I get the feeling that you misunderstood what they were trying to communicate and prioritized literal word usage over context. They should not have said "quite authoritatively". Using "quite correctly" would have been better. "Authoritatively" was a sloppy substitute for emphatic correctness.

I acknowledged upfront that the tourist could well be correct. That addresses the possibility that it was merely sloppy wording with that intended meaning.

Looking again at what you'd put earlier, your acknowledgement very much seems to have the not-total-impossibility of them being correct as a throwaway caveat, not as a real consideration of the situation in any sense. I suspect that it being used now to address that they were using sloppy wording is a retroactive understanding after I pointed it out, and by luck is a plausible explanation.

You suspect incorrectly. And I am done with this discussion.