CD's by religion

[I spent the winter writing songs about getting better]

This would be pretty tricky. Ohio in recent years has liked electing Catholics to Congress more often than we "should" based only on Catholics as a percentage of the population for some reason. It would be an interesting exercise to gerrymander Ohio trying to maximize the number of Catholics in Congress (and one I may try ). Still, the southeast is pretty much a Catholic dead zone so it probably isn't possible. The only chance of getting a Catholic in that area is to try and gerrymander Charlie Wilson back into office, so it would be an Ohio River ConservaDem pack. It may require a slice of Youngstown just for good measure. Does it count if I just try and get rid of Protestants while trying to put Eastern Orthodox Zack Space back in?

Then we also run into the problem of several incumbent Protestants who would be difficult to gerrymander out: Mike Turner (though the Ohio GOP tried to give him the boot anyway), Jim Jordan, Steve LaTourette, and Marcia Fudge. LaTourrette is packed into his own little corner so I wouldn't know what to do with him. And what to do with the VRA black seat? That’s not going to elect a Catholic! I guess the best chance would be to try and slice it up so Kucinich wins it. OH-10 is probably the most Catholic district in the state so if we could draw Kucinich into an OH-11 primary white enough for him to win, while keeping the bulk of OH-10 intact, that could be ripe for an unnamed Catholic. It’s been a while since either party has nominated a Protestant for that seat and it might be majority Catholic. Stivers would be easy to eliminate by simply creating a pack seat for Kilroy, who’s Catholic.

On the other hand, trying to draw a map to minimize the number of Catholics would be rather difficult since so many of Ohio’s influential representatives are Catholic. Where would we even begin with Cincinnati? All three current reps in the area are Catholic, as is the Democrat waiting in the wings to unseat one if a Dem-friendly map is drawn. The northwest would be awfully hard too, since Kaptur and Latta have districts that are difficult to mess with. You could try pairing Latta and Jordan, but what can you do with Kaptur besides combining her with Kucinich? A follow-the-lake seat is pretty likely to elect a Catholic, so you’d have to draw some nasty arm into Amish Country or something.

He's not talking about electing actual Catholics or Protestants but having a demographic majority, aka having all the seats in a state be majority Catholic or majority Protestant. The seat could still in theory elect someone from the other group (or even a Mormon or Jew or something), but that's not the relevant question, similar to how Steve Cohen still represents a "black" district, while my congressman is black but it's still clearly a majority white seat.

[I spent the winter writing songs about getting better]

Not quite, think of states with large Hispanic populations for starters (might be possible to draw three Protestant seats in New Mexico actually, but it'd be REALLY ugly.) Also I think he's asking majority, not plurality.

In Minnesota where the numbers basically mirror the US numbers (not the mainline/evangelical Protestant numbers though)

MN-01: Probably majority Protestant, there are some staunchly Catholic areas though and probably enough unaffiliated to maybe drop it below 50% and only plurality Protestant. Wish the Census had data on this.
MN-02: Definitely majority Protestant. Megachurches + WASP-y suburbanites + not many "ethnics" or minorities. (By WASP-y I mean more middle to upper middle class Scandinavians and Germans than the traditional definition which a few years ago I polled on and was concluded they are not WASPs, however I think it's worth noting they have kind of the same status in the Midwest that actual WASPs did in the northeast. I remember reading a demographic analysis of the ELCA once, and it was hilariously WASP-y. Even I was shocked to learn that 97% of ELCA members are white.) Carver and Scott counties have Catholic traditions but those have been diluted by the exurbanites moving in, many of whom are Catholic but a majority of whom are either WASPy or megachurchers.
MN-03: Same as MN-02.
MN-04: Well St. Paul has a lot more Jews, and non-Christian Asians, and unaffiliated, and some Irish neighborhoods, the suburbs are probably more Catholic than the other districts because of this, might be only plurality Protestant, bet it's still a plurality though.
MN-05: This is interesting, you have relatively high numbers of Jews and Muslims, and no doubt higher than average unaffiliated, but also not many "ethnics" like Irish or Italians unlike most major cities, instead a lot of Scandinavians. More Hispanics than the rest of Minnesota though. I'm going to guess Protestant plurality, but it's really splintered.
MN-06: This has a lot of Catholics around Stearns county and the exurbs are historically Catholic but have been overrun by megachurchers, lots of unaffiliated here according to most studies actually, not many mainline Protestants, there's a lot of ELCA churches but I'm guessing they're the type of that have about only 50 people that regularly attend who are mostly gray-haired and afterwards privately complain about how that new young pastor is far too liberal (BTW something like 80% of ELCA seminary students are Democrats according to some poll. And 38% of ELCA clergy support gay marriage, that doesn't sound like a lot today, but it was a poll of clergy about five years ago. And all of ELCA clergy, not just young ones.)
MN-07: Unquestionably majority Protestant. Scandinavian Lutheran country galore.
MN-08: Lots of Scandinavian Lutherans but a non-insigificant number of "ethnic" Catholics, likely majority Protestant but it's probably fairly close. Maybe even just plurality Protestant with about 15% unaffiliated.