Texas Rep. Ron Paul's insistence that states should have the final say on social issues such as abortion and gay marriage does not sit well with Bob Vander Plaats, the head of The Family Leader.

Paul was the only GOP candidate at a forum over the weekend hosted by Vander Plaats' group opposed to amending the U.S. Constitution to define marriage as a heterosexual union.

Also appearing at the Thanksgiving Family Forum in Des Moines, Iowa were Newt Gingrich, Rick Santorum, Herman Cain, Rick Perry and Michele Bachmann. Former Massachusetts Governor Mitt Romney was invited but did not attend. Also not in attendance was former Utah Governor Jon Huntsman, who has not placed an emphasis on Iowa.

Paul, who has previously said he is personally opposed to gay people marrying, said that the role of government is to preserve liberty, not mold people or society: “The law can't reflect the morality of the people. If you do that, you have embarked on something where you sacrifice liberty.”

In analyzing the candidates' performances, Vander Plaats, a vociferous opponent of gay marriage, didn't sound impressed.

“I think he let his libertarian view trump his moral compass,” he told the Des Moines Register.

Paul has also declined to sign the group's 14-point anti-gay marriage pledge.

(Related: Rick Perry signs The Family Leader's anti-gay marriage pledge.)