Very shortly after I became persuaded of Unitarianism, as I mention in my article explaining my change of mind, I realized that when I was a Trinitarian, I felt no deep need to understand the complexities of the Trinity, because the Deity of Christ, being very simple, made sense to me, and I thought it was very easy to prove from Scripture.
Later, after reflecting, and dialoguing with others, and surveying the topic more deeply, I realized that such an attitude is extremely common. Essentially, most Trinitarians who know about at least a little bit about Christianity and the Bible hold to something like the following view with respect to the Father and Jesus:
Then, they will notionally claim to be "Trinitarian", and not really give the doctrine much thought, beyond very shallow, creed-like affirmations, such as "three Persons in one Essence", without explaining what a Person or Essence is, or concerning themselves with any of the other actual difficulties that the doctrine produces. In short, it is not being serious. It is being irresponsible, and paying lip service to a doctrine which they do not really understand, and then neglecting to ever study it.
So, my challenge to you, if you are a Trinitarian, is to move beyond notional affirmation of the Trinity, and beyond simply affirming the Deity of Christ. You owe it to yourself, and have a responsibility before God, to be able to justify and explain, in detail, why what you believe is not Tritheism or Modalism, especially if you are going to call Unitarians like myself "heretics", "non-Christians", etc. Understand the difficulties with the various Trinity theories, and be able to speak about them with some precision, using the philosophical language which your framework demands that you use, all the while comparing what the Trinity theories say about God, with what the Bible says about God. Go beyond affirming the Deity of Christ, and actually try to reconcile that with Monotheism.
And if during your research, you run into one of many statements like the following, and find yourself asking, "is this type of thing really our religion?":
Christian Theology, by Millard Erickson - Chapter 14
We do not hold the doctrine of the Trinity because it is self-evident or logically cogent. We hold it because God has revealed that this is what he is like. As someone has said of this doctrine:
Try to explain it, and you'll lose your mind;
But try to deny it, and you'll lose your soul.
Then perhaps you will be more open to approaching the Unitarian view of Scripture, or at the very least, having more grace and understanding for those who hold to Unitarianism.