You are so refreshingly straightforward! Most opponents of educational choice hide behind a welter of abstractions and complicated distinctions designed to hide what is really going on. You candidly admit your premises, and I appreciate that. You say that "the establishment clause necessarily requires that government 'disfavor' religion in relation to secular programs." You accuse me of trying to "rewrite" the establishment clause to say that the government should "neither favor nor disfavor religion." In other words, I think the Constitution requires neutrality toward religion; you think it requires the government to exclude religious institutions from the benefits of public programs.
That is the crux of our disagreement over vouchers. If the Constitution requires neutrality, then a neutral program of educational vouchers is constitutional. If the Constitution disfavors religion, then vouchers that include religious schools are unconstitutional.
You declare that you "do not know where in the establishment clause [I] find such a remarkable anti-discrimination proviso." Let me tell you. I find it in the decisions of the Supreme Court.
In its most recent pronouncement on the issue, the court upheld remedial education assistance to poor children attending religious schools on the ground that the aid was "allocated on the basis of criteria that neither favor nor disfavor religion" (Agostini vs. Felton, 1997). My very words. For almost 30 years, the Supreme Court has repeatedly held that the establishment clause blocks government action that both "advances" and "inhibits" religion (Lemon vs. Kurtzman, 1971). This principle of neutrality has been affirmed time after time, including by the most liberal justices. Justice Hugo Black wrote, "State power is no more to be used so as to handicap religions, than it is to favor them" (Everson vs. Board of Education, 1947). Justice Harry Blackmun wrote: "Neutrality is what is required. The State must confine itself to secular objectives, and neither advance nor impede religious activity" (Roemer vs. Board of Public Works, 1976). Justice Sandra Day O'Connor wrote, "The Religion Clauses prohibit the government from favoring religion, but they provide no warrant for discriminating against religion" (Kiryas Joel vs. Grumet, 1994). Even Justice William Brennan, whom you call "an unreconstructed separationist," wrote that when a "subsidy is conferred upon a wide array of nonsectarian groups as well as religious organizations in pursuit of some legitimate secular end," it is permissible under the establishment clause (Texas Monthly, Inc. vs. Bullock, 1989).
Perhaps the clearest explanation comes from Justice Thurgood Marshall. He held that when government assistance "flows to religious institutions ... only as a result of the genuinely independent and private choices of aid recipients ..., is 'made available generally without regard to the sectarian-nonsectarian, or public-nonpublic nature of the institution benefitted,' and is in no way skewed toward religion," it is permissible (Witters vs. Department of Services, 1986).
The Wisconsin Supreme Court precisely followed Justice Marshall's reasoning when it upheld the Milwaukee voucher program. In that program, the state provides a voucher to the parents of poor children, and they have the right to choose what kind of education their children will receive. The voucher serves a legitimate public purpose (education) and is wholly neutral between religious and nonreligious choices. To the extent that government aid flows to religious schools, it is solely as the result of private decisions. As Justice Marshall explained, "[T]he fact that aid goes to individuals means that the decision to support religious education is made by the individual, not by the State."
In every case for the last 20 years, the Supreme Court has upheld neutral programs of aid to education (including religious education), with two exceptions. The two exceptions were overruled in 1997. The idea that government must "disfavor" religion is contradicted both by the court's decisions and by the fundamental logic of the First Amendment, which leaves religious choices to individuals, families, and private institutions--without promotion or inhibition by the government.