dungbeetle,
The problem here is that the WT is following the custom of the Jewish Christians in the group that were still keeping the Law. They wrote Paul about their beliefs and he is responding. Paul refutes their arguments and quotes from their letters but no one notices this kind of back and forth banter that we use in our posts all the time.
Forget the personal pronoun I that Paul uses when he quotes their view as the information that follows is simply being quoted from their letter and does not represent Paul's view. He refutes such material after listing it with a single word or phrase like we do here all the time but punctuation and biblical format hides such facts.
What this shows us all is that the Watchtower does not have a clue as to what the scriptures teach and cannot even read or interpret the text in an intelligent way. They bungle these texts badly taking the opposite view to the one intended. Real dummies but it is a crime that so many people have fallen victim to them and have given up their lives to such ignorance.
Joseph