(CNN) -- Accusations of blame abounded Thursday, a day after a 28-year-old man who had volunteered for a center that serves gay, lesbian, bisexual and transgender people was taken into custody for allegedly shooting a building manager at the headquarters of a Christian conservative group.
"Let me be clear that Floyd Corkins was responsible for firing the shot yesterday," Family Research Council President Tony Perkins told reporters in Washington about the suspect. "But Corkins was given a license to shoot an unarmed man by organizations like the Southern Poverty Law Center that have been reckless in labeling organizations hate groups because they disagree with them on public policy."
Perkins said the SPLC "should be held accountable for their reckless use of terminology that is leading to the intimidation and what the FBI here has categorized as an act of domestic terrorism."
Prosecutors said they are still investigating the motive behind the shooting, and the motive could determine whether Corkins is charged with domestic terrorism or hate crimes.
In a statement, the Southern Poverty Law Center described as "outrageous" the suggestion that it had contributed to the attack.
The Family Research Council, which focuses on family and anti-abortion issues and religious liberties, recently supported Chick-fil-A President Dan Cathy, who had become embroiled in controversy after making comments in support of traditional marriage.
"We are very much supportive of the family, the biblical definition of the family unit," Cathy told The Baptist Press in an interview published July 16. "We are a family-owned business, a family-led business, and we are married to our first wives. We give God thanks for that."
The statement sparked an uproar, with activists saying that Cathy voiced opposition to gay marriages.
Corkins, who was carrying 15 Chick fil-A sandwiches in his bag when he was taken into custody, "has strong opinions with respect to those he believes do not treat homosexuals in a fair manner," authorities said in the complaint filed against Corkins, citing the suspect's parents, with whom he lives in Herndon, Virginia, outside Washington.
Asked what evidence he had linking the center to the shooting, Perkins referred to the Chick-fil-A matter.
"You have seen Family Research Council listed in many of those stories -- that Chick fil-A supports and underwrites the Family Research Council.
"And in those stories where it says the Family Research Council, it says they're a certified hate group by the Southern Poverty Law Center. We've seen that term used increasingly over the last two years and it marginalizes individuals and organizations, letting people feel free to go and do bodily harm to innocent people who are simply working and representing folks all across this country."
He said the company donated $1,000 to the Family Research Council "a number of years ago" but does not underwrite his group.
The Family Research Council says it promotes "faith, family and freedom in public policy and public opinion."
National Organization for Marriage President Brian Brown also criticized the Southern Poverty Law Center, saying that its listing of the Family Research Council on its website was equating the group with violent extremist groups.
"The responsibility is on the shooter, but we need to have a civil debate over issues like redefining marriage," he said Thursday on CNN's "Early Start." "But we should not be attacking and labeling as hate groups those that we disagree (with). We should condemn violence of any sort, but we should also be responsible."
In its statement, the SPLC said it had listed the Family Research Council as a hate group since 2010 "because it has knowingly spread false and denigrating propaganda about LGBT people -- not, as some claim, because it opposes same-sex marriage."
"The FRC and its allies on the religious right are saying, in effect, that offering legitimate and fact-based criticism in a democratic society is tantamount to suggesting that the objects of criticism should be the targets of criminal violence."
The SPLC criticizes the Family Research Council for asserting, "in Perkins' words, that pedophilia is 'a homosexual problem' -- an utter falsehood, as every relevant scientific authority has stated. An FRC official has said he wanted to 'export homosexuals from the United States.' The same official advocated the criminalizing of homosexuality."
Perkins was using Wednesday's shooting "to pose a false equivalency between the SPLC's criticisms of the FRC and the FRC's criticisms of LGBT people," the SPLC said. "The FRC routinely pushes out demonizing claims that gay people are child molesters and worse -- claims that are provably false. It should stop the demonization and affirm the dignity of all people."
One legal expert said Perkins seems to be inconsistent in deciding which battles to pick.
After Dr. George R. Tiller, a Kansas abortion provider, was shot dead in May 2009, Fox News Channel host Bill O'Reilly came under criticism for having called him "Tiller the baby killer."
Referring to O'Reilly, Perkins announced in August that year that "We're going to give him an award for his courage in exposing the truth behind the late-term abortion industry."
"I wish Perkins would not use a double standard," New York University Law School Professor Burt Neuborne told CNN in a telephone interview. "When opponents of abortion engage in astonishingly bellicose speech where they call people 'murderers' and they virtually encourage people to take their lives and some nut acts on it, Perkins keeps his mouth shut. I don't see him criticizing that speech. The truth is, you can't pick and choose what kind of rhetoric to condemn."