James Dobson on Friday staunchly defended his comparison of Nazi torture experiments on humans to stem-cell research.
His comments on a Focus on the Family radio broadcast Thursday sparked an uproar among research advocates across the country.
"I made a statement that is being spun like a top by the ultra liberals who don't care about unborn life," Dobson said on the air. "Life is not high on their agenda. So why should it surprise us that they're mad at me for supporting life?"
Several local and national organizations demanded Dobson apologize for the remarks, which they labeled "offensive" and "inflammatory."
John Hlinko, founder of Washington D.C.-based research advocacy group StemPAC, said at least 1,000 people sent e-mails seeking an apology from Dobson.
"It really did seem to create a firestorm," he said.
"What really ticked us off is the Nazis killed millions of people and stem-cell researchers are trying to save millions of lives," Hlinko said.
In his broadcast, Dobson called experimentation with human embryos "Nazi-esque."
"It will lead inevitably later to cloning and ultimately to the harvesting of body parts," he added.
Michael Huttner, executive director of Denver-based ProgressNow.org, said he was disappointed by Dobson's refusal to apologize.
Huttner said almost 300 people joined a petition seeking an apology on the ProgressNow.org website and that at least 40 newspapers across the country have covered the story.