What is this fallacy?

A's statement is a conclusion. No analysis needed. B's better response is to ask: based upon what evidence do you draw your conclusion. However, B said if you cannot provide evidence, I am not a hypocrite. The "I am not a hypocrite" is an error. As Sagan famously said, lack of evidence is proof of nothing. The best B can say is A does not have evidence to establish the proposition --- which may be true even though A lacks evidence.

Can you please cite where and when Carl Sagan famously wrote or said, "lack of evidence is proof of nothing"? I cannot find a single instance where that is a direct quote.  While he did write a great deal about the nature of evidence, and or, lack thereof, it had a very specific contextual application e.g. extra-terrestrial life, implying we could not conclude life on other planets is non-existent because we do not yet have the capability of determining that yet. He did indeed write that "absence of evidence is not evidence of absence", although, the quote is not exclusively his, nor does it mean the same thing as the misquote you are paraphrasing.    

https://www.quora.com/What-did-Carl-Sagan-mean-when-he-quoted-a-fellow-cosmologist-who-said-absence-of-evidence-isnt-evidence-of-absence-Did-he-agree-with-him

The actual quote by Carl Sagan appears in his book The Demon-Haunted World: Science as a Candle in the Dark and is part of a discussion of various logical fallacies (in this case, the “appeal to ignorance” fallacy):

Appeal to ignorance—the claim that whatever has not been proved false must be true, and vice versa (e.g., There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist—and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we're still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence.