Liberals are not right about much but they are correct about this. We do have and have always had a "Living Constitution." Tradition, legal precedent and popular opinion have always trumped what is codified in the constitution as the supreme law of the land.
That the Supreme Court "interprets" the constitution, that justices are hermeneuticians, is the greatest falsehood in American politics. Justices go with the wind. Sometimes before the wind, sometimes behind, but always, long term, with the wind.
The question conservatives pose of "Where is that in the constitution?" gains nothing. Doesn't matter what the constitution says. Never has, never will. Rights are more than the constitution. The founders knew that. They expected people to demand those unwritten rights people assume they have be honored. And that has been the case. Only way to change it is to change what rights people believe they hold.