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Someone's race is not a factor in his ability to serve in the military because it's a passive trait, but homosexuality requires active behavior and that makes it a potential barrier to unit cohesion in the military, former Pennsylvania Sen. Rick Santorum said Sunday, distinguishing between an earlier argument against integration in the Armed Forces.

Explaining his opposition to the repeal of don't ask, don't tell, the defunct military policy that prohibits gays from serving openly in the military, the 2012 Republican presidential candidate said the two situations are "very, very different."

"I mean, we are talking about people who are, you know, simply different because of the color of their skin, not because of activities that would cause problems for people living in those close quarters," said Santorum, considered one of the most socially conservative candidates in the race.

But pressed on his position in an interview on "Fox News Sunday," Santorum was asked to respond to a quote that sounds similar to an argument he gave to a gay soldier who questioned his position during the Fox News/Google debate last month..

"The Army is not a sociological laboratory. Experimenting with Army policy, especially in time of war, would pose a danger to efficiency, discipline and morale and would result in ultimate defeat," reads the quote from Col. Eugene Householder.

Householder was writing from the Army Adjutant General's Office in 1941, arguing against allowing blacks in the military.

Unfazed by the similarity of Householder's argument to his own, Santorum said being gay and being a minority are not comparable.

"It's not the same. And I know people try to make it the same, but it is not. It is a behavioral issue, as opposed to a color of the skin issue, and that makes all the difference when it comes to serving in the military," he added.

Santorum said members of the military live in close proximity to one another, and by necessity must shower together in the barracks or out in the field.

That makes some people uncomfortable, he said, and "it could hurt our ability to retain and recruit and to put the best fighting force in place."

"You're talking about the ability for people to be able to have that unit cohesion, to be able to work together in a efficient fighting way," he said.

And while the 2011 and 1941 arguments may sound similar, that does not make the gay agenda a civil rights cause, he said.

"I know the whole gay community is trying to make this the new Civil Rights Act. It's not. It's not the same. You are black by the color of your skin. You are not homosexual necessarily by -- obviously by the color of your skin or anything -- it's by a variety of things."

Many members of the gay community and the American Psychiatric Association say homosexuality is biological. Supporters also note that the volunteer force is made up of individuals who best demonstrate self-discipline.

But Santorum said straight individuals won't volunteer if they are asked to serve in a place where it is uncomfortable to be.

"The idea that somehow or another, that this is the equivalent, that being black and being gay is simply not true. There are all sorts of studies out there that suggest just the contrary, and there are people who were gay and lived a gay lifestyle and aren't anymore. I don't know if that's a similar situation -- I don't think that's the case with anybody that is black," Santorum said.

Santorum placed third in Saturday's straw poll at the Values Voters Summit in Washington, D.C., with 16 percent. He followed Rep. Ron Paul of Texas, who won 37 percent in the non-binding poll, and Georgia businessman Herman Cain, who came in second with 23 percent.