The Constitution provides no right to be free from public expression of religion. The relevant portion of the First Amendment reads: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof." The basic idea is this: There should be no national religion, because establishment of a national religion would necessitate shutting down other religions. The idea that the First Amendment bans all public reference to God or Jesus is absurd. As former Chief Justice William Rehnquist famously wrote in his Wallace v. Jaffree dissent (1985), "It seems indisputable from these glimpses of Madison's thinking, as reflected by actions on the floor of the House in 1789, that he saw the Amendment as designed to prohibit the establishment of a national religion, and perhaps to prevent discrimination among sects. He did not see it as requiring neutrality on the part of government between religion and irreligion."
There is no right to be free from public expression of religion, but there is a Constitutionally protected right to free exercise of religion. Brittany McComb was chosen to speak not because she was religious, but because she had a 4.7 grade point average -- and it is none of the school district's business whether she chooses to invoke God, Jesus or Zeus (though history indicates that the ACLU would fight for her right to invoke Zeus).
The federal judiciary is noticeably more open to obscenity than religion. Laws barring public obscenity have been struck down on the grounds that passersby may "effectively avoid further bombardment of their sensibilities simply by averting their eyes." (Cohen v. California, 1971) The very mention of God, by contrast, crushes all resistance, according to the federal judiciary.
In fact, the judiciary is noticeably more open to irreligion than religion; those who propose neutrality between religion and irreligion willfully ignore the fact that state-sponsored irreligion remains the dominant mode of expression in many state-sponsored activities. State schools routinely preach the moral acceptability of sexual promiscuity and homosexuality -- but the ACLU and its buddies on the federal bench are always there to protect schoolchildren from a classroom display of the Ten Commandments.
McComb wasn't the only one disappointed by the school's decision. Four hundred graduates and their families jeered as the school cut the microphone. Aside from the precious few Michael Newdows of the world who feel that the name of God merits complete and total redaction, the rest of the country jeers along with them. Unfortunately, the federal judiciary is averting its eyes.