When the Supreme Court on Monday declined to take up the issue of same-sex marriage, the move allowed gay men and women to wed in as many as 11 new states. For Brian Brown, the president and co-founder of the National Organization for Marriage, the court’s action was the latest in a string of disappointments in his group’s efforts to stop the spread of gay marriage nationwide.

“It’s not the way our system is supposed to work, and we’ll be re-doubling our efforts to fight for a U.S. constitutional amendment defining marriage as the union of a man and woman. The very form of our government, a Republican form of government, is at stake,” Brown said.

Since its founding in 2007, Brown’s Washington, D.C.-based nonprofit has financed and assisted ballot initiatives to impose same-sex marriage bans in dozens of states as well as to vote out lawmakers, including judges in Iowa and Republican representatives in New York, who have supported letting gays and lesbians wed.

NBC News recently spoke with Brown, a father of eight, a Catholic convert [from being a Quaker] and Philadelphia resident, about the road ahead for same-sex marriage foes.

NBC: What do you make of the Supreme Court’s decision not to hear any of the gay marriage cases this term?

Brown: It’s disappointing and puzzling. What the court is essentially allowing to happen is for lower courts to redefine marriage and accept this idea that in 1868 with passage of the 14th amendment [which guarantees due process and equal protection under the law], we had gay marriage, it’s just no one knew it. That’s absurd, it’s false, but the court is now allowing these lower courts to force same-sex marriage on a number of states who have overwhelmingly voted to support the traditional definition of marriage.

NBC: How did you become one of the leaders of this movement?

Brown: I was an executive director of a group called the Family Institute of Connecticut. Although we were focusing on a number of issues, the same-sex marriage issue rose to the fore. There was a real push to redefine marriage and proponents of same-sex marriage had a pretty sophisticated political strategy of targeting champions for marriage, trying to defeat those who supported traditional marriage.

And they were having some success, and proponents of marriage as the union of a man and a woman really weren’t organized in the same sort of fashion that they were. Proponents, those that wish to redefine marriage, had the sort of state version of super PACs. They were doing everything.

I witnessed firsthand the very real need of having a national group focus on the marriage issue and helping groups be more active in lobbying and having a PAC and working on a more public policy level, rather than only on the educational level on the issue of marriage.

NBC: From there, you were part of the Proposition 8 campaign? [Prop 8 was a 2008 ballot initiative that made same-sex marriage illegal in California until it was declared unconstitutional by federal courts.]

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Brown: That was a tremendous victory. That's one part of what we've been successful at are these public votes. But we've also been very active in issue ads, cycle after cycle in congressional campaigns, presidential campaigns, states, U.S. Senate, some state and local. We continue to be involved in all of those even though what got much more attention was the ballot initiative fights.

NBC: Many people who get involved with this issue have a personal connection to it, say, through a family member? Do you?

Brown: When I started [at Family Institute of Connecticut], initially this issue was not going to be our only or main issue. The more that I learned, the more committed I was to standing up. It didn't have to be personal in the sense of any family member or anything like that. I mean, obviously I have friends and family who fundamentally disagree with me on the issue. But it was right.

When something is so true, and there are such clear consequences to a falsehood being put into the law, there's an obligation to stand up and speak truth to power.

Right now I think folks who look at this issue and think that NOM or any of the groups out there supporting the traditional definition of marriage, that we’re the Goliath, and the pro-gay marriage Human Rights Campaign [NOM’s main foe] is the David -- they've got the story in reverse. They are one organization among a whole platter of organizations like Freedom to Marry, GLAAD and all of these other groups that have almost unlimited access to the media and get their talking points across largely for free.

But for us, it's a lot more difficult and we're up against a much bigger hurdle. I actually sort of relish that. It doesn't matter to me whether it's easier or harder or whether we have less money or more money. The real question is: are we standing up for the truth in marriage? And I've never had any question about that.

NBC: The Human Rights Campaign put out a list of “Exporters of Hate.” And you are on their list. How do you respond to that?

Brown: What the Human Rights Campaign is doing is false. It's sad. It's in my view caustic to a civil society, in leveling those you disagree with as bigots or haters or outside the realm of acceptable public opinion.

Generally, those of us who believe in a free and fair exchange of ideas don’t believe in that as a solution to an argument. We believe in a free and open debate. As long as we stand up and refuse to be cowed by this sort of intimidation, the more Americans see that, the more they reject it.

NBC: NOM’s 2012 990 tax form (the latest available) for its 501(c)(4) shows ending the year in the red with a $2 million deficit. It was the largest number so far compared to previous years.

BROWN: True. I think it's very simple. If you look at 2010, you'll also see a deficit and we were a smaller organization at that time. 2008, you'll also see a deficit. We pride ourselves in putting the money that we have into the fight. We don’t have a lot of employees -- twelve employees -- and for our size, we have a relatively large budget. That's because we put the money where it will be most effective. Every election year, we're going to show a deficit, because we're putting our money where it should go.

(Editor's note: NOM's education fund -- a 501(c)(3) -- had a surplus of $1.6 million in 2012)

NBC: It seems you have been doing more international trips and going overseas to talk about your work?

Brown: There is another falsehood in HRC's report that somehow we're folding NOM into a new International Organization for Marriage (IOM).

In every country, there's a group, if not similar to NOM, somewhat like it. And so obviously, because we're in this fight together, I've been talking to all of those folks. We've had these discussions and we floated the idea but there's no formal structure. Even if it does get created it's not going to be supplanting NOM.

So the notion that this is a new front and that we're leaving the fight in the U.S. to fight internationally it's just merely a concocted story.

NBC: If the court says we think there should be same-sex marriage you think this will unleash another Roe v. Wade moment? Will NOM continue to push its argument?

Brown: There is so much to do. We've only begun to get our argument out into the public square. We can take a lot of hope and a lot of encouragement from the (anti-abortion) movement. The (anti-abortion) movement in the two years following the decision in Roe v. Wade was largely in disarray. We look at the movement as it is now, but don't remember that it was a very difficult time. Again, this movement is not going to go away, it's going to continue for our children and grandchildren far into the future.

NBC: Some people who don't support gay marriage say they "hate the sin, love the sinner." What are your own views on LGBT folks and what (marital) right should they be granted?

Brown: It's a non-sequitur to say that if you have gay friends or gay family that you must support same sex marriage. The first question isn’t about whether you have friends or family who are gay. The first question is what is marriage? And what marriage is, is the union of one man and one woman. I still have friends who would identify as gay and say, 'We totally disagree with Brian. Brian is wrong on this but we can still be friends.' I think increasingly though that's becoming harder and harder because the language of the other side is one of demonization and so, have I seen some change in these relationships? Of course I have.

This interview has been edited.