As a rule, Protestants don’t like being called “Protestants,” or to be identified with any organized denomination. They like being called “just Christians.”
Of course there are always exceptions, and some Christians will proudly announce, “I’ve been Southern Baptist all my life.” or whatever.
But the big trend in Protestantism right now is to disassociate oneself from “organized religion” and “denominations.”
(This could be a good thing for Catholics involved in outreach, BTW. At least we don’t have to struggle against denominational loyalties like we used to.)
Many denominations who plant new churches don’t name their churches “Main Street Baptist Church.” (or whatever the name of the denomination is.) Instead, they will name the church “Main Street Community Church” or something that hides the denomination. Other examples would be “The Friendship Church,” or “Calvary Chapel.” etc.
The justification is that people don’t want to be part of “denominations” anymore, they just want to be “Christians.”
And many (non-Catholic) Christians don’t join churches anymore. They go from church to church, enjoying music at one church, teaching at another church, fellowship with friends at still another church, and getting involved with charitable works at still another church!
Isn’t that amazing? But it’s true.
I know a lot of you disagree with all of this. I know I do. But that’s the way it is in Protestant Land, and all our disagreeing won’t make a fig’s worth of difference. If we rail against it to our Protestant friends, we will just alienate ourselves and not build any bridges, but instead, tear them down.
“Christian” is always the correct term. Follow it up by the statement, "A Christian who attends “Name of Church.”
For example, before I became a Catholic, I was “a Christian who attends ____ Evangelical Free Church.”
Now I am “a Christian who is a member of the Catholic Church.”
If the Christian does not attend any church, then they are “a Christian who does not attend any church,” or “a Christian who attends church as they feel led.”
There is a difference, BTW, between “membership” in a Protestant Church and just “attending” a Protestant Church. Many Protestant Churches don’t push membership anymore. It’s all part of the same trend–getting away from man-made, organized religion.