Hi Patrick,
“Protestant” is a term that I mainly hear used by Catholics to refer to those faith traditions that were born of the Reformation, much in the same way that people of the Jewish faith might refer to non-Jews as “Gentiles”.
Just like most “Gentiles” would prefer to be called by something more precise and positive, like “Catholic”, “Orthodox”, “Anglican”, or some other term, the word “Gentile” is a simple and handy word from a Jewish perspective to denote everyone who is not a Jew. It’s quick and easy.
Likewise, most “Protestants” prefer to be called by their faith tradition (i.e. Baptist, Methodist, Lutheran, Assembly of God, etc) or just “Christian” because it is more precise and denotes something they are for, not something they are against.
The vast majority of us “Protestants” were born into our faith tradition and we are not protesting anything, except maybe the word “Protestant”.
I assume you are Pro-life, right? So am I. How do you like to be called “Anti-choice”, which is what the pro-abortion rights folks call us? We justifiably prefer to be called “Pro Life” because that is what we are for. That is the best analogy I could come up with for how it feels to be called “Protestant”.
As for OSAS, I think it is mainly the fundamentalist faith traditions who believe that (like Southern Baptists), but there may be others.