As the great steamroller of secularism rumbles towards them, Christians generally have become much less mindful of denominational differences between them. Unbelief and Leftist oppression have become the current enemies for all Christians. So true Protestants (NOT including Anglicans and other "social" churches, who are generally too "modern" to believe in anything much) appreciate the solid opposition to abortion and homosexuality from Catholics, for instance. And Christians do need to band together. The secular steamroller has largely crushed belief and church loyalty in Britain, Western Europe and Australia. Only in the USA, Russia, Poland and Latin America is belief in the risen Lord still strong.
Young people therefore may not know that Protestant/Catholic rivalry was once intense -- and not long ago at that. Within living memory we were all rather like Ulstermen.
When I was a kid I went to a State (government) school and the Catholic school was just down the road. And we all used to walk home in those days -- none of that namby-pamby nonsense of parents picking us up. So there was opportunity for us to get into mischief. And one sort of mischief was that the kids from the two schools used to chant sectarian rhymes at one another. I suppose it was better than coming to blows. I remember the rhymes very well but I am a bit embarassed about it all now so I will repeat only one of the rhymes: "Mary, Mary, mother of God, baked a cake and it was a sod". Apologies from my 70-year old self for my 10-year old self.
And at that time Protestants and Catholics even tended to go to different shops. Two big Department stores in Brisbane exemplified that: McWhirter's and T.C. Beirne's. Protestants shopped at McWhirter's and Catholics shopped at T.C. Beirne's. It actually felt weird to go into the "wrong" one of those.
And the thought of a Catholic marrying a Protestant was quite rage-provoking. A Protestant father contemplating one of his children marrying a Catholic would utter the most dire warnings against it and back up the warming with threats of disinheritance etc. Catholics were equally vehemently against "intermarriage" but would acquiesce in it as long as the children of the marriage were brought up Catholic.
Now here is the amusing thing: Despite all the rage and heartburn, young Catholic and young Protestant people still married one-another at a great rate. I take some interest in genealogy and when you look at genealogical records in Australia, the number of intermarriages is astounding. It is true of my own relatives and forebears, of course. I have both Irish and English ancestry. Young Catholics and Protestants clearly found one-another fascinating. Forbidden fruit? That could be part of it.
There is a rather good novel by Ruth Park called "Harp in the South" about a Catholic family in Australia about 100 years ago which captures it all rather well. There are two friends -- one Catholic and one Protestant -- who get on very well with one-another -- except on one day of the year -- the day when the Orange order marches and they sing of how "King Billy slew the Papish crew at the battle of Boyne water" etc.
So even in the old days there was goodwill lurking, despite different traditions -- JR