This was not a major point of dispute until Fr. Feeney.
I am an ardent flat earther, and I do believe you can say it is part of the faith. However I will never get so worked up about those who believe the globe, because I am not autistic, and at least try to normal and charitable to my fellow novus ordo'ite /protestant neighbor who doesnt have a clue. Because there were a lot of things in my life that I did not have a clue about.
It's called treating others the way you would like to be treated. Gee I wonder who said that one time.....
So the main issue is the utterly eccentric and hyper excited behavior of the feenyites going around pretending like their fellow trad is on a secret mission to get them to renounce their belief in all that the Church has taught.