I'll start by stating up front I know nothing about William Giraldi beyond what he has written about himself in his July/August (2015) New Republic piece "Confessions of a Catholic Novelist." With that said I have to say my impression of him is rather low. He seems to be very self-obsessed and very ignorant of a topic you would assume he at least knows a little bit about.
He starts off from the very first line being hyperbolic and arrogant.
"It’s not altogether easy being a Catholic, and it’s immeasurably harder being a novelist, so you might imagine the myriad conundrums of being both." I can't say I was all that interested in imagining what he wants since the very first thing to pop into my head was a fairly basic question: in comparison to what? What makes being a Catholic any more difficult than abiding by other belief systems? What makes being a writer an especially difficult profession? Giraldi never successfully answers either of these. What he does succeed in doing is exposing his poor understanding of literary criticism and study.
Virtually every example he gives fails completely. Almost every author he writes about either went out of their way to make more of their Catholicism than any one else every did or they are authors who have been so thoroughly studied that no aspect of their life and times has not been examined. Their religion being just one more piece of that review. If this was the only flaw in his piece it wouldn't be worth bothering with but he goes even further in various places. He creates a false impression and then tries passing it off as factual.
Another line that irked me quite a bit was his patently false statement:
"More to the point, you won’t find a novel by Malamud or Roth or Bellow subtitled “The Adventures of a Bad Jew,” and even if you did, you wouldn’t have to prep yourself to be preached at (revisit Roth’s story “The Conversion of the Jews” to see for yourself)."
Bullshit. You can find literary pieces with that type of title. For instance after roughly a minute to two minutes perusing Google I found a review of a contemporary play entitled "Bad Jews." As for content, Catholics are not the only ones to produce either self-deprecatory works or preachy screeds. Just knowing an author's religious preferences doesn't immediately lead me to assume anything about their writing. That it clearly does bias Giraldi is no reason for him to project that onto anyone else. Yet, he does without a second thought.
There isn't anything in Giraldi's piece that can't be easily refuted and attributed to a lack of intellectual honesty. There's nothing automatically wrong with having strong opinions or even slipping into a woe-is-me self important stance but if that's all you've got why bother?