I admit I have not read this lengthy article but our LCMS church has former Catholics.
I'll admit that I've but skimmed the article but both our Deacons are former Protestants.
70% of America is Protestant, or unchurched but from Protestant background.
25% of America belongs to a Protestant church (let alone attends one.)
Therefore, 45% of Americans are unchurched Protestants.
27% of Americans are Catholics, or are unchurched but from Catholic backgrounds.
23% of Americans belong to a Catholic church.
The number of Americans belonging to a Catholic church has been growing steadily.
Therefore, about 4% of Americans are unchurched people from Catholic backgrounds. Another 13% are Catholics who do not attend Church regularly.
Given the fact that unchurched Protestants so vastly outnumber unchurched Catholics, isn't it strange that such a preponderous portion of Protestant "converts" are from Catholic backgrounds? Why can't Protestant outreach ministry reach their own?
A few suggestions:
Catholics actually do believe that the bible is the source of their faith, and continue to believe it after they quit church. Catholics fall away largely because they dislike the moral requirements; they've lost faith in the Church, not in the bible; they just don't know how to live up to the bible. Protestant apologetics typically presume a belief in the inerrancy of the bible. This is an effective basis for converting such "disobedient" Catholics, allowing them to find the Christianity and community they miss and the faith they still believe in, but either without the moral structures they dislike, or with better instruction in living up to them. It is, however, useless for converting non-Christians, since appealing to the bible as a source for arguments is only effective if people believe in the bible. It's a hard habit to break; the New Testament's apologetics were largely written to Hellenized Jews who had already accepted the validity of the scriptures, so it's the method of evangelism familiar to sola-scriptura types. This is why the stereotype of "bible-thumping" exists.
Advice to Protestants: to convert non-Catholics, focus on meeting and enlarging the godly desires instilled into all men.
Advice to Catholics: to retain Catholics, or expand their faithfulness, forget all the social justice crap. Focus on how to overcome foibles, sinfulness, and doubt.
We have quite a few in my LCMS parish also. Many left during the sex scandals (it was pretty bad in Davenport before the house cleaning started).