Is this some sort of remnant of evangelical puritan protestant ideology?
I don't understaun this.
If you ask me, it'd make as much sense as Orthodox and Christians.... or Shia and Muslim...
I know not all Christians are Catholics but for feck's sake...
They're all Christians to me....
Edit:
It's a U.S thing but this is the sort of things I hear...
https://www.gotquestions.org/Catholic-Christian.html
I am a Catholic. Why should I consider becoming a Christian?
I now know more distinctions (apparently Catholicism requires duty and salvation is process, unlike Protestantism?) but I still think they're of a similar branch (Christianity) so I just wonder the social factor
Probably because depending on the context "Christians" is likely referring to "Protestants." There are some very significant differences between Catholic and Protestant Christianity, moreso than between Protestant denominations, whose differences tend to be a bit more trivial. Other comments make some good points, but it is not too far of a stretch to say that Catholicism may be different enough to be considered a separate religion (I don't know who gets to draw these lines). But in the most technical sense, yes, Catholics are a subset of Christians.
I believe what you mean to say is that Protestant sects would be considered a separate religion, as Catholicism far predates other sects.
All Catholics are Christians, but not all Christians are Catholics. They are a subset by definition.
What I think they meant was that categorizing Catholicism as a seperate religion from Protestantism while Prostestantism claims Christianity makes no sense considering that Catholicism has an older claim to being Christian.
So, if anyone shouldn't be able to claim "Christianity" because of being a new, differentiated religion then it should be Protestants. Using that logic it should be "Christians and Protestants".
But I agree, they are all in fact Christians.