Here's the reason that whenever someone says "I was raised a Catholic, so I know what it teaches," what follows will be the weirdest farago of nonsense you will ever hear.
According to the research blog of the Center for Applied Research in the Apostolate:
And a handy graph to prove the point!//In comparison to the Pew study, D'Antonio et al. find that half of self-identified adult Catholics (50%) are unaware that the Catholic Church teaches the following about the bread and wine used for Communion: "the bread and wine really become the body and blood of Jesus Christ." However, 63% of adult Catholics, regardless of what they think the Church teaches, believe that "at the Consecration during a Catholic Mass, the bread and wine really become the body and blood of Jesus Christ."As shown below, this creates four groups. The largest are "knowledgeable believers," representing 46% of adult Catholics, who are aware of the Church's teachings about the Real Presence and say they believe these to be true. Additionally, there is another 17% who believe in the Real Presence but who are unaware that this represents a Church teaching. These are the "unknowing believers."The second largest group is the "unknowing unbelievers" who do not believe in the Real Presence (i.e., they believe the bread and wine are only symbols) and do not know that this represents a teaching of the Church. There is something hopeful about this group, which represents a third of adult Catholics (33%). Even though they currently do not believe the Church's teaching, they may come to believe it if they knew and understood it better. Knowledge and belief of this may even bring more of them to a Catholic parish on Sundays.What is rare, representing only 4% of adult Catholics, is someone who knows about the Church's teachings regarding the Real Presence and who states they do not believe this teaching to be true. These are the "knowledgeable doubters" (...note that this study uses the same methods of CARA Catholic Polls, e.g., anonymity, self-administered response without an interviewer, which limit social desirability bias).