Marriage benefits are a subsidy towards a particular social arrangement (and it changes all the time, mostly through the shape of tax and divorce laws). You don't have to hate anyone to be against extending it. There are supporters and opponents of beef subsidies but cow hate is not the major driving force there.

Of course, politics is not about policy http://www.overcomingbias.com/2008/09/politics-isnt-a.html so it's very difficult to successfully argue anything because the argument (on any political topic, and in any direction) will almost always be disingenuous.