Offense, however, does not equate to coercion. Adults often encounter speech they find disagreeable; and an Establishment Clause violation is not made out any time a person experiences a sense of affront from the expression of contrary religious views in a legislative forum, especially where, as here, any member of the public is welcome in turn to offer an invocation reflecting his or her own convictions. See Elk Grove Unified School Dist.v.Newdow, 542 U. S. 1, 44 (2004) (O’Connor, J., concurring) (“The compulsion of which Justice Jackson was concerned . . . was of the direct sort—the Constitution does not guarantee citizens a right entirely to avoid ideas with which they disagree”).
Justice Kennedy thus rejects the idea that the First Amendment confers "freedom from religion," at least in the public sphere. As long as prayers don't "denigrate nonbelievers or religious minorities, threaten damnation or preach conversion," the Supreme Court advises Americans to lighten up.
The gist of Justice Kagan's dissent is that the First Amendment obliged Greece to be more aggressively inclusive. In her view, it wasn't enough for the town to issue its invitation; officials should have sought out and actively recruited representatives of diverse faiths to deliver opening prayers in order to live up to their avowed pluralism. Governments have a positive obligation to cultivate pluralism that Greece, in Kagan's view, has not fulfilled. Kagan also accepts, as Kennedy doesn't, that a preponderance of Christian prayer in a public forum has a tendency to stigmatize non-Christians who refrain from bowing their heads and so on, although Kennedy points out that any such tendency was not acted upon in Greece. Kagan and Justice Alito, who wrote a concurrence to Kennedy's opinion chiefly to dispute points in Kagan's dissent, see the power of prayer very differently. Kagan seems to see sectarian prayer as inherently divisive in a way remedied only by programmed diversity. Alito recalls a Founding moment when the Continental Congress squabbled over opening prayers but finally recognized that prayer could be unifying regardless of which denomination's representative gave the prayer. To him it's a big deal that puritanical Sam Adams proposed that an Anglican open the first session. The moral, it seems, is that Sam wasn't offended or subject to coercion by hearing an Anglican prayer. But Sam also knew that the Anglican wouldn't be the only divine praying over Congress, so how was he different, apart from his initial concession, from the religious minorities in Greece? For Alito, the difference boils down Greece's "clerical employees [doing] a bad job in compiling the list of potential guest chaplains." That doesn't rise to the level of a constitutional case in his view: "[A] unit of local government should not be held to have violated the First Amendment simply because its procedure for lining up guest chaplains does not comply in all respects with what might be termed a “best practices” standard." Kagan suspects that this was not a mere "bad job," while Alito (and Kennedy) presume good faith, so to speak, on the part of the Greeks. That's where we're stuck, it seems, until a critical mass of Americans rises to demand a new constitutional understanding of the necessary limits on religious expression in the halls of government in a time of greater and more irreconcilable religious diversity than most Founders could have imagined or desired.