I don't know who Marcus Grodi is. (sorry)
But I think if you had to provide proof that there are 33,000 protestant denominations that are very distict and separate, you would have a very difficult time indeed. I am providing a link of those supposed 33,000 denominations you can see that they are often times only separated by distinction of location. http://66.102.7.104/search?q=cache:3XISpAa6nnMJ:www.adherents.com/+adherants+denominations&hl=en&gl=us&ct=clnk&cd=1
Using Grodi's method of identifying distinct denominations, we can see there are many, many separate listings for Catholic Church (in addition to the following list, there are also listings under Russian othodox, orthodox etc....):
Catholic: 1,100,000,000 (2121 recs.)
Catholic - affiliated
Catholic - Albanian Catholic Church: 1,405
Catholic - Alexandrian Rites: 385,065
Catholic - Antiochene Rites: 3,381,484
Catholic - Antiochene/Syrian Rites
Catholic - Armenian Catholic: 334,860 (3 recs.)
Catholic - attend at least monthly (18 recs.)
Catholic - attend regularly (8 recs.)
Catholic - attend weekly (16 recs.)
Catholic - Augustinian: 4,500 (2 recs.)
Catholic - Belarussian Catholic Church: 30,000
Catholic - Benedictine
Catholic - bishops (56 recs.)
Catholic - black (7 recs.)
Catholic - black congregations
Catholic - Bohemian parishes
Catholic - born-again (2 recs.)
Catholic - brothers (2 recs.)
Catholic - Bulgarian Catholic Church: 20,000
Catholic - Byzantine Rites: 8,995,048 (3 recs.)
Catholic - Capuchin
Catholic - Carmelite: 13,000 (2 recs.)
Catholic - Carthusian (2 recs.)
Catholic - Celestines
Catholic - Chaldean Catholic Church: 308,409 (5 recs.)
Catholic - Chaldean Rites: 3,588,995 (3 recs.)
Catholic - churchgoers (5 recs.)
Catholic - Cistercian (15 recs.)
Catholic - clergy (5 recs.)
Catholic - Cluny Order (4 recs.)
Catholic - colleges and universities (2 recs.)
Catholic - Coptic Catholic: 192,955 (3 recs.)
Catholic - Czech Catholic Church
Catholic - Dominican
Catholic - Eastern Rite: 12,000,000 (2 recs.)
Catholic - Ethiopian Catholic: 192,110
Catholic - evangelical
Catholic - foreign language parishes
Catholic - Franciscan (9 recs.)
Catholic - French parishes
Catholic - German parishes
Catholic - Greek Catholic: 2,300 (7 recs.)
Catholic - Hispanic
Catholic - Hungarian Catholic Church: 280,750
Catholic - Indian language parishes
Catholic - Italian parishes
Catholic - Italo-Albanian Catholic Church: 61,597
Catholic - Jesuit: 25,000 (8 recs.)
Catholic - Knights of Columbus: 1,600,000 (2 recs.)
Catholic - Krizevei Catholic Church: 48,937
Catholic - Latin Rite: 997,000,000 (19 recs.)
Catholic - Lithuanian parishes
Catholic - Malankarese Catholic
Catholic - Maronite: 2,948,949 (14 recs.)
Catholic - Melkite Catholic Church: 1,073,340 (2 recs.)
Catholic - miscellaneous language parishes
Catholic - missionaries
Catholic - nominal (2 recs.)
Catholic - non-Roman: 16,700,000 (3 recs.)
Catholic - nuns (66 recs.)
Catholic - official
Catholic - other (17 recs.)
Catholic - Pentecostal: 80,000,000 (16 recs.)
Catholic - Polish parishes
Catholic - practicing (8 recs.)
Catholic - priests (64 recs.)
Catholic - priests, diocesan
Catholic - priests, religious
Catholic - Redemptorist
Catholic - Redemptoristine
Catholic - Romanian Catholic Church: 1,423,800
Catholic - Russian Catholic Church: 4,000
Catholic - Ruthenian Catholic Church: 495,888 (2 recs.)
Catholic - secular apostolic institutes: 15,000
Catholic - seminarians (49 recs.)
Catholic - seminarians, major (2 recs.)
Catholic - Slavic parishes
Catholic - Slovak parishes
Catholic - Slovakian Catholic Church: 229,190
Catholic - Spanish parishes
Catholic - Syrian Catholic Church: 109,547
Catholic - Syro-Malabarese Catholic Church: 3,280,586 (2 recs.)
Catholic - Syro-Malankara: 322,988 (2 recs.)
Catholic - Trappist (4 recs.)
Catholic - Trappistine (2 recs.)
Catholic - Ukrainian Catholic: 5,323,841 (29 recs.)
Catholic - Uniate (16 recs.)
Catholic - Ursuline (2 recs.)
Catholic - Vietnamese parishes (2 recs.)
Catholic - white
Catholic - Xaverian Brothers
Catholic Alliance
Catholic Apostolic Church (Irvingites) (7 recs.)
Catholic Apostolic Church at Davis
Catholic Apostolic Church in America (7 recs.)
Catholic Charismatic Renewal
Catholic Christian Church (2 recs.)
Catholic Church of the Apostles of the Latter Times (2 recs.)
Catholic Golden Age
Catholic Life Church
Catholic Patriotic Church
Protestants are not broken up into 33,000 distict denominations any more than the Catholic Church is broken by the above "denominations."
Major Denominational Families of Christianity
Branch Number of Adherents
Catholic - 1,050,000,000
Orthodox/Eastern Christian - 240,000,000
African indigenous sects (AICs) - 110,000,000
Pentecostal - 105,000,000
Reformed/Presbyterian/Congregational/United - 75,000,000
Anglican - 73,000,000
Baptist - 70,000,000
Methodist - 70,000,000
Lutheran - 64,000,000
Jehovah's Witnesses - 14,800,000
Adventist - 12,000,000
Latter Day Saints - 12,500,000
Apostolic/New Apostolic - 10,000,000
Stone-Campbell ("Restoration Movement") - 5,400,000
New Thought (Unity, Christian Science, etc.) - 1,500,000
Brethren (incl. Plymouth) - 1,500,000
Mennonite - 1,250,000
Friends (Quakers) - 300,000
(Catholic: Includes Old Catholic, Aglipayan (Philipines), Uniate, in addition to the Catholic Church headquartered at the Vatican. Occasionally "Catholic" is used, as in the table above, to refer to a branch of Christianity that includes the Catholic Church headquartered at the Vatican, as well as relatively recent off-shoots that still consider themselves Catholic, such as the Old Catholic churches. Certainly it also includes non-Latin Rite Catholic churches such as Uniates, Greek Catholics, Ukrainian Catholics, Maronites, etc., all of which are in full papal communion and regarded as part of the same religious body as the "Roman Catholic" church. The fact that there are non-Latin Rite Catholics such as these is one of the reasons that many Catholics do not like the term "Roman Catholic Church" as a name for their church. While "Roman Catholic" has long been used without any offense intended, it is increasingly disliked by some members of the Vatican-based Catholic Church, and in nearly every place on this web site that this church is mentioned, the term "Catholic Church" is used. "Roman" is left off, as both inaccurate and potentially objectionable. On other pages, the term "Catholics" by itself refers to members of the Vatican-based Catholic Church, whether they be Roman Catholics, Greek Catholics, Ukrainian Catholics, Uniates, Coptic Catholics, etc. )