The Rapture is a belief held by a small minority of Protestants. But it's not unlike RCs to paint all Protestants with the same brush.
Even still, eschatology is not a salvation issue. Not on the order of, say...bowing down to the stock of a tree or praying to dead people or sacrificing Christ anew with every Lord's Supper.
Actually, the timing of the Rapture is more the issue I believe. Most Protestants believe in the Rapture (from the Latin Rapturo, meaning to "catch up") in that they believe Christ will return to be joined together with His bride. She will meet him in the air. Some believe that this has somehow already occurred. Some believe it will occur prior to the period known as the Tribulation. Some believe it will be prior to the wrath of God being poured out. Some believe it will be at the end of the Tribulation. And some people don't see a literal 1000 year reign yet believe in the return of Christ. Some may even allegorize the catching up. That is why I emphasized that I wasn't discussing timing. I just wanted to know if he believed that Christians would be gathered together to meet Christ in the air. His answer was that he believed whatever his church taught and didn't have to interpret Scripture himself. This answer was received after a monster picture was posted from someone in the Protestant camp who ignorred Scriptures admonitions about nobody knowing the day nor the hour. This same picture was represented as Protestant belief and a joke made up by Protestants. But as you say, it is a secondary doctrine.
I'm sure it's splitting hairs, but that particular quote was put up by someone who is NOT RC, I believe. Any stick will do.
"The Rapture is a belief held by a small minority of Protestants"
Yes, but it is held by a large part of the Baptists and Pentecostals.