The identity of the person and their association with their statements is a matter of public record. Even if we were to assume that the individuals held copyright to their letters, the government claims no copyright and using excerpts for the purpose of advancing the debate would appear to fall under "fair use". The authors have voluntarily associated their names with their letters as part of the public record; if you wanted to abbreviate their names as a courtesy you could of course do that, but they don't realistically have any expectation of privacy in their names being associated with their statements.