When I first met Father Thad I was a Baptist minister and he was the priest at the neighborhood Catholic parish. A complete stranger to me, he popped into my office and stated that he must use our church baptistery. A brief reminder about baptism: Baptists practice baptism by immersion. They dunk converts completely under the water.
Typically, Catholics practice sprinkling or pouring. And that is just the beginning of the differences between these two faith traditions on the issue. The theological meaning reinforcing the practice of baptism puts the camps even farther apart.