In July 1997, his concerns about children potentially being exposed to pornography on the Internet led him to start Filtering Facts, a nonprofit organization that encouraged libraries to voluntarily adopt filters. Burt's advocacy included testifying as an expert witness in the library filtering case "Mainstream Loudon v. Board" in 1998; before the National Commission on Library and Information Science; as well as state legislatures, city councils, and local library boards. This activism was profiled in an article in "The New York Times" in 1999.