Libertarians may be cheering, but not for the reasons you state. They are cheering the fact that the USSC has struck down a law that, in contravention of our Bill of Rights and respect for individual liberties, had nevertheless existed for too many years.
The Bill of Rights never spelled out a generalized sodomy right, unless the 10th Amendment is an anything-goes wild card. Not even the most libertarian of the founding fathers would have bought the notion that states had to respect sodomy rights.