Assuming you're referring to this question:
As you see, the question is not put on hold or closed as off-topic and you've got two answers. Your question has also has a rate of +2, which is not bad.
Asking about the authenticity of any quote is on-topic as you see here; there are 122 questions.
However, there are many cases where the community dislikes the question, maybe because sometimes it doesn't really matter whether X said Y or maybe because the OP already found evidence while asking the question.
There could many reasons why your question was not well received and one reason has been explained by Oddthinking:
I don't know why it was downvoted, but I wonder if it is because there is little reason for doubt here. The idea that he said it is a fairly prosaic claim. The Politifact article discusses how they actually asked Sabato to substantiate the quote, and he did so, in a way that they conclude is "Mostly True". Why wouldn't you provisionally accept this rather prosaic claim as true, given the substantial evidence you've already discovered?
