A friend recently posted a quote that sounded so inflammatory that I wanted to confirm its authenticity. I googled it and found many instances of it being repeated but never the actual source. When I mentioned this it started a increasingly contentious thread about what makes a quote authentic.

My friend's position is that if it was in quote marks in a mainstream publication, then it's a quote. I contend that it needs some sort of citation that indicates when and where it was said.

Is there an accepted standard in this field that people follow?

Here is the quote in question: "The idea is to put the Palestinians on a diet, but not to make them die of hunger." Dov Weissglass

What is important to me is to very clearly establish the line that divides hearsay from a confirmed quote. Thanks.