@peacefulpete
I think the NT has its own, unmistakable origin that is not dependent on any other text (outside of the OT). But that doesn't mean there aren't arguments for the opposite claim - like what you cite above. For me, it's a matter of choice. I choose the Bible...
So I am answering "theologically", not based on the results of literary analysis, as that may indicate otherwise. I would liken it to the question of creation and evolution; the question of finality of life and eternal life, etc. etc.
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Going back to the cross or stake with the JWs, I think they are "trapped" in their methods of dealing with the NT-text. If I compare the issue of the cross and, for example, the exile of John on the Isle of Patmos, at their core, both are (relatively) insignificant issues that do not change the meaning and implications for salvation, then regarding the cross, JWs will strenuously "argue" about how Jesus did not die on the cross, but if you ask them where in Revelation it says anything about the exile of John on the Isle of Patmos, they will remain silent. Because there is no mention of exile anywhere. Yet they claim he was there in exile. Remember the picture of John in bonds, in their commentary on Revelation? How can they portray something that is not in the NT text? They wave their hands that it is irrelevant. But it's like they're depicting Christ on the cross...