There seems to be a growing trend in many circles where people feel that in order to preserve scriptural purity, they turn to history to see if the Roman Catholics are credited with or at least agreed with doctrines that were carried over from the reformation.
The Trinity is one of the most popular of the doctrines under fire. There's another thread on here wherein people do the same to Christmas and even Sunday as a day of gathering to worship as opposed to the Fri-Sat Sabbath. And the reason they reject things aren't really based on a synthasized study of scripture but by isolating scriptures that seem to support their private interpretation and then justify and try to shock the reader into adopting their tradition's view by saying, "Rome did it. They have their finger prints all over it." And of course the stigma out there in protestant land is that anything Rome touched seems to be "corrupt".
However, as I hinted at above, most of this is just a rejection of Roman Catholic Tradition and a replacement of that tradition by substituting their own tradition.
If you study all the heresies that the church confronted, such as Modalism, Arianism and Nestorianism, you'll find that a great amount of effort and scriptural integrity went into the way in which they defended themselves from these heresies.
However, when you ignore the past you are often susceptible to fall into the same errors that plagued the early Church.
By trying to rid yourself completely of any of the Traditions that to the common eye seem "Catholic" you wind up throwing out the baby with the bathwater and are forced to replace those traditions with your own. This in turn color the way in which you interpret what you read.
That's why we have Calvinists and Lutherans and Wesleyans etc. I mean, they each teach conflicting things from one another and yet, they have followers. People agree with the Lutheran tradition and believe it to be more accurate than the Calvinists and so on. And even the folks that seem to call themselves "non-denominational" are still faced with coming up with an interpretation as to what they read means and then "teaching" that interpretation, despite the fact that their non-denominational teaching conflicts with what the non-denominational church down the street teaches.
I'm finding that the great irony in all of this are the scriptures themselves. If people merely try to rid themselves of things that are "later" additions and not commonly held beliefs during the time of the disciples, then even the canon of scripture comes into question.
The New Testament as we know it today didn't really come about until nearly three/four hundred years AFTER Our Lord's ascension to sit at the Father's right hand.
Now, if a group were really to get back to basics and experience the Faith as those that met the Apostles had, they would have to make due with reading the OT and re-examining all the writings that were in broad circulation in the Christian population for that three/four hundred years. A daunting task!
My point is only that the Trinity ought to be understood, not by trying to juxtapose your tradition's teachings onto what you believe to be "Roman Catholic" but instead to go back and read what all went into and exactly who those Christians were that, led by the Holy Spirit, decided upon the NT canon.
Further, if you're protestant, it wouldn't hurt to look at the OT canon as you know it in comparison to the OT canon as the Roman Catholics and the Eastern Orthodox knew it. I mean, to be fair, the protestant OT canon is foreign to those first Christians that heard the good news, not by reading, but by hearing and worshiping side by side the likes of St. John, the beloved.
Don't just toss out the Trinity and construct your own theology on the Godhead based on an emotional reaction to anything supposedly Roman Catholic. I mean, if you don't even know what a Modalist is, how can you tell that you aren't one? What's so bad about being a modalist? Why did that same group of people (not talking about Roman Catholics as we know them today) that decided upon the NT canon view modalism as a bad thing? You agree with them about the canon but aren't familiar with their thoughts on the Godhead? Well, I invite you take a look. God's blessed us with the internet. Google your hearts out in search of the Truth.
I would start with St. Athanasius work titled, On the Incarnation and see if you don't see that there is reverence and depth and a zealous appreciation for Holy Scripture in those writings.
Put "Athanasius On the Incarnation" in the google search field. The first result that pops up is the entire text hosted on a Reformed* website, translated by an Anglican and has a foreword by C.S. Lewis (talk about cross-denominational!).
Just for the record, I'm an inquirer at an Eastern Orthodox church but seeing as many confuse the Orthodox with Roman Catholics, I figured St. Athanasius work being hosted in such a denominationaly varied way is testament to the fact that not everything that people accuse the Roman Catholics of corrupting is truly corrupt. Think of the fact that the very NT you revere wasn't in circulation or even written and gathered into books until hundreds! of years later. The word bible isn't in the bible either, just as the Trinity, and yet that's not something we hold against it.
Glory to Jesus Christ