If someone lies, it is proper to say that he or she is a liar. You don't like this. Too bad.

Your "millions of Catholics believe" is an example of the logical fallacy of the Appeal to Popularity.

When the magisterium taught that slavery was morally acceptable, it should have been followed without question. Also when the magisterium taught that women are inferior to men, that was also truth. When the magisterium taught that freedom of of religion was "an insanity", you would have accepted it. When the magisterium taught that all non-Catholics were damned, you would have said "Yes!"  And now that the magisterium teaches the exact opposite on all of these, it also teaches objective and eternal truth.

No, the only way you can do this piece of double think is by lying to yourself or by ignoring historical fact.