David Blankenhorn's reversal on gay marriage has saddened Brian Brown, the president of the National Organization for Marriage (NOM).

Blankenhorn, a prominent opponent of gay nuptials, wrote in an op-ed that “the time has come for me to accept gay marriage and emphasize the good that it can do” and “Whatever one's definition of marriage, legally recognizing gay and lesbian couples and their children is a victory for basic fairness.”

In 2010, Blankenhorn, the founder and president of the conservative group Institute for American Values, served as an expert witness in favor of California's gay marriage ban at the trial challenging the constitutionality of Proposition 8.

Brown, who helms the nation's most outspoken group opposed to marriage equality, insisted that Blankenhorn had been pressured to abandon his opposition.

“David Blankenhorn has suffered extraordinary vilification and abuse as a result of his writings in support of marriage as the union of husband and wife and his testimony in defense of California's Proposition 8,” Brown wrote at his group's blog.

“It is sad when a powerful and compelling voice goes silent – especially when the topic is one as important as marriage, and where the silence is not motivated by a change of view about the nature of marriage but rather a seeming succumbing to the continual pressure of the cultural elite. Yet retreating from the debate is not a path we or our followers will ever travel, for retreat will surely lead to defeat. We intend to fight on, and fight harder, for the truth – that marriage is the unique union of a man and a woman.”