Here's (
http://www.rts.edu/Site/Resources/FacultyArticles/OneBaptismRevised.pdf) an interesting article that I've passed along when asked, as a long-time visitor to a couple of Reformed Baptist churches, if I will submit to rebaptism.
What if the Lord can take what is meant for what we would call "evil" (the baptism of a newborn in the RCC, albeit a Trinitarian baptism) and turn it to good, for His own purposes, some years later when the person is born again? The second birth was, after all, within God's eternal plan from before the foundation of the world.
Years ago, R. C. Sproul, Jr. wrote a very polemical article against the RCC and former Catholics in "Tabletalk" that brought tears to my eyes - and there's no love lost between the Catholic Church and me. It was harsh and as an ex-Catholic, I was wounded. I wrote to him - and he wrote back. In the final paragraph of his letter, he told me to "go back to Rome."
I have not followed that instruction.