So Mulcahy claims that literary criticism is written in such an obscure way that only other literary critics can decipher it. Mulcahy wants literary criticism to be more accessible to normal people.

However, the text tells us that his main point is not accessible to all, but can only be discerned by a select few! This makes him just as bad as the other critics he is criticizing. Mulcahy, then, is part of the problem. He is complicit, and his points are only discernible to other critics: the very community he is impugning.

Why is "inform" not an answer?

I thinks inform means providing information
inpugn means questioning.
He is trying to questions the critics why their critics are so abstruse or difficult for a normal person to understand.

Mulcahy, in averring that most literary criticism has become so filled with abstruse jargon as to be practically indecipherable to anyone save its practitioners, is himself (i) ______: his main point will be discernible only to the very community he seeks to (ii) _____ .

The reflexive pronoun "himself" before the blank indicates that he is guilty of the very crime he accuses the others of. Therefore, complicit is the best word.

ALSO

The part of the sentence after colon informs us of the word for the first blank. The phrase "his main point will be discernible only to the very community", further strengthens complicit as the right choice.

And since he has criticized the practitioners of literary criticism, who are referenced by "very community", the word for the blank must be impugn and not merely inform.
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