First, they will attempt to resort to the "historical" reality of the Trinity, and more broadly with the concept of monotheism in the Bible. Except this approach is logically and factually flawed on at least three levels:
1. Monotheism is not the historic understanding of the Bible or the New Testament in particular. As Trinitarian Michael Heiser wrote:
Monotheism as it is currently understood means that no other gods exist. This term isLikewise, as we have demonstrated in the previous post and abundantly elsewhere, the existence of many real gods is taken as a given. Jesus and God the Father are immediate examples. But 1 Cor 8:5-6 or Acts 17:18 ("strange gods", Gk daimonion, a technical term used by the Greeks, here by philosophers to describe the relationship of Jesus to salvation and the resurrection, indicating their perception of Jesus as a second god as described by Paul), or Romans 8:16 make it clear that real, divine beings, plural, do exist and more will exist as mankind is saved. Jesus himself quotes Ps 82:6 in his preaching in John 10:30-38, referencing the OT teaching that men can become gods. His argument is only valid if they really do become gods like God, or else he is in fact guilty of blasphemy in his equating of himself with God.
inadequate for describing Israelite religion, but suggesting it be done away with would no doubt cause considerable consternation among certain parts of the academic community, not to mention the interested laity. Henotheism and monolatry, while perhaps better, are inadequate because they do not say enough about what the canonical writer believed. Israel was certainly monolatrous, but that term comments only on what Israel believed about the proper object of worship, not what it believed about Yahweh’s nature and attributes with respect to the other gods.
2. No single scripture or passage can be used to explain the relationship of the heavenly beings ("host of heaven", a phrase firmly built upon the Ugaritic terminology defining the Council of Gods, wherein Elohim presides) or relationship of Jesus and God the Father as being of one substance. By contrast, passages such as John 17 or Philippians 2:5-9, or especially John 1:1 are all clearly written to explain the relationship of Jesus and God, and from these passages there is no hint of some kind of sharing of essence.
3. It is impossible to maintain "monotheism" when the early Christian writers explicitly teach the salvation we seek is to become divine ourselves. Nearly without exception 2 Peter 1:4 is used by every early Christian writer, including the Father of the Trinity Athanasius, to state that men will become gods, just as Jesus was god and became man.
Secondly, the number of scriptures teaching the real existence of multiple real gods are so many as to be overwhelming. I looked up in a searchable online Strongs Concordance the following: "host/s of heaven"(20+), "Lord of hosts"(285), gods, in a real sense, not idols, (about 10), angel of the Lord, which was often a divine being (64), angel of God (10 times). Don't forget that Jesus himself is called an angel in Rev 10.
Of course, there is Deut 32:8, 43 where the text was plainly altered to attempt to conceal the fact there are the 70 sons of God, just as in the Ugaritic texts, given authority over the various areas of the Earth, and Jehovah is given Israel as his portion by the Most high God.
The proof of the lack of proof is the insertion of the bogus text of 1 John 5:7-8, which attempts to describe the workings of the Godhead in Trinitarian terms. Problem is it was added to the Latin text 250 years after John penned the words, and 1500 years later in the Greek.
So I would invite people to throw down their best two or three Trinitarian proof-text verses, and I will interact with them. But I will require they explain Deut 32:8-9, Ps 82/John 10:30-38 and John 1:1. No outside commentaries or sources, other than grammatical or lexical sources to accurately explain the text. I am sick to death of hearing the ignorant phrase "the passage must be examined in the broader context of the entire Bible." No, not so much. There was no compiled Bible until the 4th Century. The OT was much more fluid than it is today as well. And if we want to go to the "broader context", then Trinitarians can make this really short, because nearly all scholars of all beliefs, Christian, Catholoic, Jewish, Evangelical, atheist or Mormon, acknowledge the context of the Bible is for a form of henotheism, meaning many real gods, but only one to be worshiped, which is monolatry. Scholars such as Michael Heiser may argue about the nature of those gods in terms of how they came into existence, but there is no doubt the Hebrews and early Christians believed in a plurality of divine, meaning godly, beings. And we haven't even touched on the fact the Hebrews fully believed that God had a wife.
So send me some passages and be willing to interact a little bit. It will only hurt your Trinitarian pride.