Catholic tradition has been changed over the years. The truth in the Bible has not. When I was in school in the good ole days, we had fish on Fridays for the 3 Catholic families in school. Then, lo and behold, they said that was no longer necessary. Then, a Kennedy wanted an annulment. He could not get one without “paying” a fee even though children were involved. I just never understood that.
The explanation for the "no meat on Friday" will be that it's just a "discipline" and not a dogma of the Roman Catholic church. Like the "rules" for fasting before Communion were. Except, I remember as a little kid being told it was a SIN to eat meat on Friday as well as how long I had to fast before communion. I still remember being about ten years old and being SO hungry before Sunday morning Mass that I sneaked a donut and then felt such remorse and fear that I went to confession as soon as I could and did penance for it. Imagine that...making a kid think she was going to hell because she was hungry and ate a little bit before Mass! When churches are guilty of "teaching for doctrines the commandments of men", they give up any claim to be the sole authority for Christians.