In the law, people aim to come to conclusions.  These conclusions can be a matter of what is or isn't constitutional.  These conclusions can be a matter of who is or isn't guilty of a crime.

Usually we assume, or very much hope, that rulings which become constitutional law are ones that have good or solid reasoning "behind" them.  Juries don't need to give their reasons for verdicts, but judges usually give their reasons for their rulings, especially in matters of constitutional law.

In this case, the justices who were part of the concurrence were split into two "camps."  (The concurrence refers to the two opinions which in this case collectively decided the case.  However, in other cases, a justice might write a decision in which he "concurs in part and dissents in part."  And, a justice can dissent from a decision on grounds similar to another dissenting opinion.  I forget if that is called concurrence of some type.)

The two "camps" agreed that the taxpayers couldn't challenge the actions of the President as a constitutional violation of their rights.  However, the two camps came to that result by adopting contradictory premises along the way to their conclusion.

In this case, the liberals (in the blogosphere)point to the mutually contradictory premises which the two right-wing camps adopted as evidence that the conclusion was poor.  Or, at least, that some reasoning used in reaching it was unsound.

The case was about 2 things:

1. whether taxpayers have standing as plaintiffs to sue the federal government for conduct they allege violates the 1st amendment;
   
2. whether the conduct violates the 1st amendment.