The argument around 1:21 says look at Mark 1:1-4
1 The beginning of the good news about Jesus the Messiah,[a] the Son of God, 2 as it is written in Isaiah the prophet:
“I will send my messenger ahead of you,
who will prepare your way”[c]—
3 “a voice of one calling in the wilderness,
‘Prepare the way for the Lord,
make straight paths for him.’”[d]
4 And so John the Baptist appeared in the wilderness, preaching a baptism of repentance for the forgiveness of sins.
[c] Which quotes malachi 3:1
3 “I will send my messenger, who will prepare the way before me. Then suddenly the Lord you are seeking will come to his temple; the messenger of the covenant, whom you desire, will come,” says the Lord Almighty.
and [d] quotes Isaiah 40:3
3 A voice of one calling:
“In the wilderness prepare
the way for the Lord[a];
make straight in the desert
a highway for our God.
If Mark is quoting Malachi and Isaiah and they are referencing YHWH and saying the messenger is preparing the way before YHWH and making straing paths for YHWH then, since we John is the messenger then Jesus is YHWH.
Rebuttals?