SPLC's criteria for listing hate groups is based on those who "demonize" a class of people with "misinformation and lies," according to Heidi Beirich, director of the SPLC Intelligence Project. Such groups include the Ku Klux Klan, anti-Semitic organizations, neo-Nazis and black supremacy groups.
"There are only a handful of anti-gay groups," said Beirich. "We don't list those who are against gay marriage or the Biblical prescription against gay marriage -- only the groups that are engaged in demonizing propaganda and lies about the gay community and basically lying about them to make them pariahs."
Previous campaigns by Public Advocate include:
A fundraising letter asking recipients to "imagine a world where police allow homosexual adults to rape young boys on the streets?"
Comparing same-sex marriage to bestiality.
Suggesting having gays as Boy Scout leaders is "the same as being an accessory to the rape of hundreds of boys."
Characterizing campaigns to stop anti-LGBT bullying as "requir[ing] schools to teach appalling homosexual acts ... force private and even religious schools to teach a pro-homosexual agenda."
Public Advocate president Eugene Delgaudio, who is head of the board of supervisors for Loudon County in Virginia, told ABCNews.com n July that the ad campaigns are only "colorful language and hyperbole." He didn't respond to a request for comment today on the suit.
Edwards and Privitere hope the incident is a teachable moment.
"We want to use this as an opportunity to educate people and show them that a gay couple can and do have loving relationships," said Edwards.
"This sort of thing has a trickle-down effect," said Privitere. "I think of all the closeted gay high school students who got mail that day and felt disheartened that they would never have a family and the parents on the fence about whether to accept their gay child for who they are. That hurts.
"These people are spreading lies, and I want them [recipients of the mailers] to know they have our support," he added.