If they completely understood Catholic Doctrine, they would still be Catholic.
Don't you think everyone has the right to hear all sides or is there something to fear from letting that happen?
If you believe this then please present the muslim side, the Hindu side, the Jewish side, etc....
The fact is you are wrong. everyone has the right to hear the truth. Prots only have part of the truth, the entire deposit of faith can only be found in the Catholic Church.
What is stunning is that Catholics are unwilling (like muslims) to examine their faith in the clear light of day.