Libertarians gave us gay marriage and abortion on demand.
Go away.
No, no, and no.
It took all of 20 minutes for the straw man argument to appear.
Republicans citing religious arguments against "gay marriage" were a much bigger cause. If Republicans had properly framed the issue, libertarians would have realized that "gay marriage" is in fact anti-libertarian. Even without laws "legalizing" so-called "gay marriage" homosexuals were free to have whatever sort of relationships they wished. What they couldn't do was use the power of government to compel other people to honor their relationships.
If Republicans had framed the issue as one of "Should homosexuals be allowed to force other people to honor their relationship in the same way they would a heterosexual marriage", very few people would have sided with the leftists. But the way the leftists framed the issue, the gay activists were able to portray the Republicans as promoting religious oppression, and the Republicans who kept citing Biblical arguments played right into the leftists hands.