I'm looking for examples where (1) the opponents of some proposed law, constitutional amendment, or judicial decision argued "this action will be interpreted in this particular bad way" or "this action will set a precedent that will be used to reach this particular bad result," (2) the supporters assured the public that no, of course this won't happen, and (3) some time down the line — preferably no more than 50 years, just to avoid especially hard questions of causation — the foretold result did take place, despite the supporters' reassurances. (It doesn't matter whether you like the ultimate result or not; and it also doesn't matter whether you think the assurances were sincere or not.)

Here are three examples, from a forthcoming article of mine:

1. In Griswold v. Connecticut (1965), the Supreme Court struck down a ban on the use of contraceptives. A three-Justice concurrence (joined by Justice Brennan) seemed to dismiss the argument that this would lead to slippage to a broader sexual autonomy right (presumably because others had been arguing about the risk of such slippage):

   [T]he Court’s holding today ... in no way interferes with a State’s proper regulation of sexual promiscuity or misconduct. As my Brother Harlan so well stated in [an earlier case in which he argued for a right of married couples to use contraceptives], “Adultery, homosexuality and the like are sexual intimacies which the State forbids ... but the intimacy of husband and wife is necessarily an essential and accepted feature of the in-stitution of marriage, an institution which the State not only must allow, but which always and in every age it has fostered and protected. It is one thing when the State exerts its power either to forbid extra-marital sexuality ... or to say who may marry, but it is quite another when, having acknowledged a marriage and the intimacies inherent in it, it undertakes to regulate by means of the criminal law the details of that intimacy.”

   Yet in the recent Lawrence v. Texas, the Court used Griswold as "the most pertinent beginning point" for its decision to strike down laws banning homosexual conduct.

2. From the 1960s on, many states decriminalized same-sex sexual conduct. Some states then banned sexual orientation discrimination in employment, housing, education, or public accommodations. Some added crimes based on sexual orientation to the list of offenses that are treated as hate crimes. Some allowed same-sex couples to adopt.

   When some such liberalizations were proposed, some people warned that these laws were steps down a slippery slope to broader rejection of traditional sexual rules, including towards same-sex marriages. These slippery slopes arguments were dismissed, sometimes contemptuously. The claim that a hate crime law “would lead to acceptance of gay marriages” was called “arrant nonsense.” A proposed antidiscrimination law, people were assured, does not “put Massachusetts on a ‘slippery slope’ toward” “legaliz[ing] ‘gay marriage.’” “Those that truly have a problem with homosexuality will see [a domestic partnership proposal] as part of the ‘slippery slope’ [toward gay marriages] . . . . But, this legislation needs to be looked at on the face value of what it is, and it really does very little.” Editorial, A Vote Against Hate, Louisville Courier-J., Feb. 3, 1994, at 6A; Editorial, A Gay-Protection Forum, Boston Globe, Oct. 15, 1989, at A30; Phil Pitchford, Council Members Wary of Partner Registry, Riverside Press-Enterprise, Apr. 30, 1994, at B1 (quoting Riverside Human Relations Commission member Kay Smith).

   Yet when the Massachusetts Supreme Judicial Court held that the state constitution requires the legislature to recognize same-sex marriages, part of its reasoning rested on the legislature’s decision to ban sexual orientation discrimination: This decision, the Court reasoned, undermined the asserted government interest in condemning homosexuality as immoral, and thus helped strip away any rational basis the law might have had. Likewise, when the Vermont Supreme Court held that the state constitution requires the legislature to recognize same-sex civil unions (marriages in all but name), a large part of its argument rested precisely on the legislature’s past enactment of various gay rights laws, including the enactment of antidiscrimination laws and hate crimes laws that refer to sexual orientation. Goodridge v. Department of Public Health, 440 Mass. 309, 312 (Mass. 2003); Baker v. State, 744 A.2d 864, 885-86 (Vt. 1999)

3. When the Equal Rights Amendment was being debated in the 1970s and 1980s (both at the state and federal levels), and the ERA’s foes argued that the sex discrimination ban might lead to legalization of gay marriage, such arguments were derided as “emotional scare tactics,” “hysterical,” and “canards.” Yet one Justice who provided the necessary fourth vote for the Massachusetts decision relied in part on the Massachusetts Constitution’s Equal Rights Amendment, which banned sex discrimination: Sexual orientation discrimination in marriage laws, he concluded, was sex discrimination. Patricia Avery & Patrick Oster, Equal Rights for Women – Doomed?, U.S. NEWS & WORLD REP., Apr. 28, 1975, at 45; Betty Friedan, Feminism’s Next Step, N.Y. TIMES, July 5, 1981, § 6, at 14; Judy Mann, Obstruction, WASH. POST, Feb. 19, 1982, at B1; Goodridge, 440 Mass. at 344-49 (Greaney, J., concurring).

I'm pretty sure the same happened with assurances that the Civil Rights Act of 1964 would never lead to, or even authorize, race-based preferences for nonwhites; likewise, as David Bernstein coincidentally posted this morning, this happened with assurances that the Civil Rights Act of 1964 would never lead to speech restrictions, or interferences with certain kinds of discriminatory practices. I've also heard the same about assurances that the income tax would never go above 10 or 20%, and that the social security number would never be used as a national identification, but I haven't seen specific quotes on this, and I like to have specific quotes.

So if you have specific quotes and specific citations that fit these conditions — (1) when a proposal was made, opponents argue that it would by its terms yield a certain bad result, or would set a precedent for a bad result, (2) supporters assured the public that this wouldn't happen, but (3) the opponents' predictions ultimately came true (or very nearly true), and the supporters' assurances proved wrong, please post them in the comments.

I'd like the comments thread to be a useful resource for this, so please keep posts within these criteria. In particular, please don't argue about whether race-based preferences in employment, hostile work enivornment law, high income taxes, national identification numbers, or a constitutional right of sexual autonomy or same-sex marriage are a good idea. That's not what this post is about. Also, please limit yourself to specific quotes and specific citations. Please avoid general conjectures about when such unreliable assurances must doubtless have been made.