Look at it this way: If the U.S. Supreme Court came out with a decision requiring all states to recognize gay marriage, it's unlikely that a single gay marriage proponent would complain. When the Supreme Court ruled last fall that sodomy laws were unconstitutional, the Court read into the Constitution a meaning that hadn't been there for two centuries - and the living Constitution crowd cheered. How is that any less "tinkering" with the Constitution than writing down an amendment?
By the way, I'm singling out liberals for a reason. Conservatives who oppose amending the Constitution are against the sort of judicial activism that rewrites the meaning of the Constitution while leaving the text unchanged. There's nothing inconsistent about being against judicial activism and against "tinkering" with the Constitution through the amendment process. You can't say the same about liberals who see the Constitution as if it were Felix the Cat's magic bag from which they can pull out any public policy they want.
Not only are the "living" constitutionalists fickle about their love for the American charter, they're deeply skeptical about democracy itself. Why is it OK for unaccountable, unelected judges to willy-nilly say the Constitution says 2 plus 2 equals 5, but it's somehow tyrannical for the House, the Senate and 50 states to debate an amendment with wall-to-wall media coverage? Why are big-D Democrats so terrified of small-d democracy?
Opponents from the McAuliffe school typically respond that a constitutional amendment is permanent, entrenching "bigotry" in the Constitution for all time.
Well, we can argue about the bigotry claim another day, but I fail to see how amending the Constitution is any more or less permanent than the changes imposed on the Constitution's meaning by, say, the Warren Court.
I bet it would be a lot easier to repeal a constitutional amendment than it would be to overturn, say, the constitutional requirement of providing criminals with Miranda warnings, which was simply invented by the Supreme Court. Meanwhile, amendments have been repealed and superceded by other amendments several times.
The trouble with "living constitutions" is that of necessity they end up having no meaning other than whatever meaning judges read into them. Dead - or "enduring" - constitutions can be changed but they must change by popular consent. Liberals like McAuliffe, however, would prefer to leave the wording of the Constitution unchanged so long as they can control its meaning.