This is my answer

In a recent post between myself and a fellow preacher, I responded by saying, “A Reformed Baptist cannot be an independent Baptist because the reformation teaches the universal church.”

To that response, a younger man (not a pastor) asked, “Why is belief in the universal church antithetical to being IFB?”

This is my answer

You've asked a fair question. The answer I think is found in our understanding of what exactly is independent Baptist. (I wish to point out that both Pastor ....... and I used the term independent Baptist, not IFB or Independent Fundamental Baptist). There are, of course, many many IFB churches that believe in the universal church. I use the term independent Baptist to mean a church that is free and independent. We have no head but Christ, we are answerable to no other but Christ. Though a church may claim to be independent and believe in the universal church, the positions are doctrinally exclusive. 

The doctrine of the universal church is that IT is the true church and local congregations are mere representations of the true (and that not perfect). 

The doctrine of the universal ( the word comes from the word Catholic) church was used by the Roman Emperor to secure his authority over all congregations in his realm. 

Those churches that rejected his authority were persecuted. Protestant doctrine never rejected the Catholic Church concept of church, they just revised it to mean an invisible, universal church. According to Protestant doctrine, that universal church maintains authority over local congregations. So, as I understand it an independent Baptist must reject any form of the universal church in order to be genuinely independent and free. 

Marvin McKenzie

In the fields