Christian conservative group American Family Association (AFA) is urging its members not to open letters postmarked with stamps honoring Harvey Milk, the first openly gay elected official of a major U.S. city.

The stamp was unveiled during a White House ceremony last week on what would have been Milk's 84th birthday.

(Related: Harvey Milk stamp unveiled at White House.)

Saying that Milk is “the last person we should be featuring on a stamp,” the group said members can do two things.

“Refuse to accept the Harvey Milk stamp if offered by your local post office. Instead, ask for a stamp of the United States flag,” the AFA wrote in a blog post, then added, “Refuse to accept mail at your home or business if it is postmarked with the Harvey Milk stamp. Simply write 'return to sender' on the envelope and tell your postman you won't accept it.”