Christ's argument here is a "how much more than" line of reasoning. If human magistrates are called "gods" who will perish, how much more is the Christ worthy of the title of God? It is self-evident, however, that Christ is God:
"In the beginning was the Word, and the Word was with God, and the Word was God." (John 1:1)
That's what the false teachers smear onto the text. He is CORRECTING THEM, explaining why "Son of God" is not "God".
"In the beginning was the Word, and the Word was with God, and the Word was God." (John 1:1)
Another standard verse toss. Does anybody bother doing just a little homework? Minimal attention is required. Take it literally, for real, because words can be used to mean anything. This verse points the direction to go. The beginning. Genesis 1:1. And there it is:
Genesis 1:1 In the beginning God [Elohim] created the heaven and the earth.
Apply a false premise and the whole argument becomes nonsense.
The usual response would be the next verses in John, because prepositions can be jerked with to twist meanings (I refer to the stand line of interpretations, which fly in the face of any knowledge of Torah whatsoever). But back to what the word Elohim means:
Hebrews 4:12 For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.