Yes, you read that right: debaptism not rebaptism. In the spirit of those now famous worldwide bus posters in the UK, the National Secular Society is now selling “certificates of de-baptism,” to those who want to definitively renounce their initiation into the Church of England. One interviewee compared infant baptism to child abuse. While I have some doctrinal problems with infant baptism, I wouldn’t go that far.
One thought does occur to me, though. If you, a secularist, really thought that your baptism was an antiquated and worthless ritual, why would you even need to go through the process of formally renouncing it?