Sorry to say there are many errors in that argument. Let me try and explain the issue in very simple and practical terms.
The Bible teaches that there is one God: YHWH. It also says that Jesus is YHWH. The Father, the Son, and the Holy Spirit are all called Lord and God, yet there is only one God - one YHWH. This is a great mystery revealed to us by God through Jesus, and the apostles and prophets. And this is not insignificant or irrelevant, but core to the Christian faith, because it boils down to this: Jesus is the visible image of the invisible God. Christians are saved by God’s grace through the person and works of Jesus Christ, and they worship Him because He is the one true God. To put it more forcefully, Jesus is not a god, He is THE GOD, and the only way to the Father. So, to deny that Jesus is God is to deny God.
The Bible teaches that whoever believes and is baptised into the name of the Father, the Son, and the Holy Spirit, will be saved, but whoever does not believe is condemned. So, to disbelieve in and deny that the Father is God, the Son is God, and the Holy Spirit is God, or to deny that there is only one God, is to deny the one true God.
The Bible teaches that whoever believes and is baptised receives the forgiveness of sins, adoption and the gift of the Holy Spirit. The fruit of the Holy Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control. Through the works of the Holy Spirit we are sanctified, that is, made Christ-like.
Quakers who follow in the steps of Hicks deny God as Father, Son, and Holy Spirit. They deny that Jesus is YHWH in flesh. As such, they deny God.
In the Quakers' Book of Discipline, they write:
"Each person must seek individual guidance and follow his own conception of God." But, the Bible teaches very explicitly who God is - Jesus Christ, God in flesh.
Here are just a few of many verses (best read in context): Isaiah 44:6 Revelation 1:8 John 10:30 Colossians 2:9 John 1:10 Romans 11:36 1 Corinthians 8:6 John 1:2 Colossians 1:15-16 John 8:58
In the Friends' Apology, Barclay writes that
"God is not divisible into parts and measures and therefore cannot be resisted nor wounded nor crucified." This goes hard against the Bible, who clearly portrays Jesus Christ, fully man and fully God, as crucified.
John 3:14 Matthew 20:18-19 John 19:18 Romans 5:8 Galatians 3:13 1 Peter 2:24
Quakers also claim that
"Scripture cannot be considered the principal ground of all truth, for the Spirit is the first and principal leader", but this is contrary to what the Bible says:
"All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be competent, equipped for every good work." To illustrate this point further, Quakers write:
"Many other Quakers draw spiritual sustenance from various religious traditions, such as Buddhism, Judaism, Islam, Hinduism, and the nature religions." and
"Most Quakers do not consider the Bible to be the final authority or the only source of sacred wisdom. We read it in the context of other religious writings and sources of wisdom." These statements are profoundly anti-Scriptural and not Christian.
You can find more in their own words here:
FAQs
There's much more I can write, but this post is already lengthy and I want to keep the focus on two things: (1) Jesus is the only way to the Father. No one comes to the Father except through faith in Jesus as God in flesh. (2) There is no inner light apart from the Holy Spirit, given only by God's grace through faith in Jesus. So, when someone who claims to have an "Inner Light" say something to the effect that Jesus is not YHWH - God in flesh - or that God is not Father, Son, and Holy Spirit, he is not speaking in accordance with the Holy Spirit, for the Holy Spirit has already spoken this in the Bible.