At any rate, a more serious answer to the OP:
Apparently, what is at stake is whether or not a set of words is to be understood as belonging to the canonical text of St. John's first epistle, and this has apparently trinitarian import. In the link that Cruciform cited, there is a discussion of whether or not the early Church fathers even quoted this particular text, and it seems (based on my skimming the article) that they may not have, even in the context of trinitarian discussion.
In answer to the question of the OP, "if it is not divinely inspired and an authoritative part of the Bible, then why is it in there," here, I think, the answer of the Muslims, of the Manicheans, and even of the Protestants themselves (when they are speaking of the deuterocanonical works of Catholic Bibles) easily could be given: "It was an interpolation!"
And I think that Bright Raven would have no answer, nor would any protestant. It seems as though he basically has two options:
1. He must accept on blind faith that the text of the Bible as he has it is the correct version. [This seems unreasonable, however; moreover, it certainly won't convince someone who disagrees.]
2. He must be open to historical evidence that some parts of the Bible may have been interpolated. He must suspend judgment altogether about whether or not his text is the "correct one," and whether any given verse in the Bible, absent compelling evidence, is authoritative and divinely inspired. [Especially so in the case of the New Testament...but then, there goes sola scriptura, right?]
These are the wages of placing your faith in a book, ripped apart from all context (historical or otherwise), and entirely divorced from any kind of living tradition (here, Plato's discussion in the Phaedrus of living discourse vs. the dead letters of a written manuscript should be taken into account (I am, of course, acutely aware of the irony of my saying this)). :idunno:
Me? I say that I have the correct version of the Bible because the bishops of the Catholic Church command me to believe it.