The man who would not praise Pindar unless he had read him would be a low, distrustful fellow, the worst kind of sceptic, who doubts not only God, but man. He would be like a man who could not call Mount Everest high unless he had climbed it. He would be like a man who would not admit that the North Pole was cold until he had been there.
But I think there is a limit, and a highly legitimate limit, to this process. I think a man may praise Pindar without knowing the top of a Greek letter from the bottom. But I think that if a man is going to abuse Pindar, if he is going to denounce, refute, and utterly expose Pindar, if he is going to show Pindar up as the utter ignoramus and outrageous impostor that he is, then I think it will be just as well perhaps--I think, at any rate, it would do no harm--if he did know a little Greek, and even had read a little Pindar. And I think the same situation would be involved if the critic were concerned to point out that Pindar was scandalously immoral, pestilently cynical, or low and beastly in his views of life. When people brought such attacks against the morality of Pindar, I should regret that they could not read Greek;....
I found the whole GKC article here.
CS Lewis says something very similar in an article about science fiction and who should undertake to review it (NOT, he says, the people who generally despise or have no sympathy for sci-fi or have no understanding of what it purports to be about).