Personally, I see the trinity as a solution to the problem of there being two Gods mentioned in the bible (other than false gods) when it also clearly states that there is only one true God. I do not claim to understand this concept but that in itself does not make it a false teaching as the WT claim. We can not expect to understand the mysteries of God and it is a presumption to insert words into the scriptures as the WT have done in order to make a particular piece of text say what they need it to say in order to balance with whatever else they teach.
Why else would they insert words? To help us understand a difficult verse? Personally, I think that they have done it in order to befuddle a really simple message. A message that is so simple that, if left to our own understanding, we would understand it. And they would'nt want that would they!
The teaching of the trinity was arrived at as a direct result of there being so many texts that clearly identify Jesus as God or a god. Weather it is 'God' (which in many cases it is) or as 'a god' makes no difference at all since we know that the scriptures clearly state that there is only one true God and all others are false gods.
It is remarkable actually how Jehovah's Witnesses are happy to believe in two gods. I believe they don't really think about it.