In that which the faithful hold in common to be the TRUE CATHOLIC FAITH, THEY ARE INFALLIBLE and "CANNOT ERR IN MATTERS OF BELIEF". -Second Vatican Council, "Dogmatic Constitution on the Church", no. 12.
Just HOW are the "faithful" able to "infallibly recognize truth"? I can tell you this: THIS is how so many of the "faithful" cannot debate honestly and openly with the Scriptures and non-Catholics. They, in their own minds, are infallible and simply CANNOT be wrong.
I think with most it is more that they believe whatever the Roman Catholic Church tells them is true and it's true because the Roman Catholic Church says it is true. They are also taught to view those outside of Catholicism as partners with Satan to draw the "faithful" away from the "true" church. So-called "heretics" were executed in the past for the crime of "stealing away the souls of the faithful" through their false teachings.
When I was about twelve, we were living on base and I went to Mass by myself. Since it was the first time there, I got the service times mixed up and sat in on the Protestant service by mistake. I kept waiting for the priest to come out and he never did and it dawned on me that I was sitting in on the Protestant service and I was too scared to get up and leave. I remember having this terrible feeling that I had sinned by going to a Protestant church! In fact, it was and may still be considered a sin to attend any church that is not Catholic.
So, as you pointed out, some here simply refuse to consider that what their church teaches about anything can ever be in error. In the occasional discussions I have with my Catholic Mom, they mostly end with her retort of, "Well, that's what we believe.". It doesn't matter that I show her from her own Bible version what Scripture says about an issue, if it goes against what she has been taught, she refuses to even think that maybe "they" were wrong. The REAL problem with that - and something Catholic leaders should keep in mind - is that far too much weight is placed on the idea of the "Church" being infallible about everything they say that, when it IS proved in inescapable ways that they HAVE erred, many may go to the opposite extreme and reject everything they were taught - even of those things where the Catholic Church is right Scripturally. The "Berean" method that Paul spoke about is there, I think, specifically as an admonition for us to do the same - prove all things by Scripture.