"What others think of us would be of little moment did it not, when known, so deeply tinge what we think of ourselves." - Paul
***
What are some historical examples of "slippery slopes" that actually slipped? - Quora
Question: What are some historical examples of "slippery slopes" that actually slipped?
Some claim the following under the 'slippery slope' argument for personal freedoms:
Legalizing gay marriage will lead to polygamy and then bestiality.
Legalizing marijuana will lead to increased use or legalization of more dangerous substances.
Creating a single payer healthcare system will lead to the socialization of more private enterprises.
Use of NDAA to one day indefinitely detain Americans.
And so on….
Does this argument have any historical merit?
Seems to me that legislation has only progressively led to good things happening, not more and more things that the majority of society considers reprehensible. Cases of actual "slippery slopes" that I can think of are instances of progressive changes of what people consider moral and ethical, like civil rights. Not a negative thing.
What are historical things where a bad thing was legislated in the area of freedoms, which lead to other bad things?
My Answer: Your question is problematic, because it presupposes that the starting action and its consequent actions must be bad.
Yet this says nothing about the mechanism of the slippery slope itself, which is what we should be looking at, since regardless of our current evaluations of the moral value of said consequences, the mechanism will be at work anyway.
Consider that what we consider to be good things nowadays were once considered bad, and that what we consider to be bad things now may one day be considered good.
For example take your example of "Legalizing gay marriage will lead to polygamy and then bestiality", and let me add incest on to it too. Yet the principles behind gay marriage (that informed and consenting adults should enjoy identical rights) can also be applied to incest and polygamy, and arguably to animals as well (at least if you're not a vegetarian - killing animals for food is surely worse than having sex with them, and this is without taking into account the suffering that animals go through when raised for human use, which non-vegans are also guilty of). So perhaps one day incest and polygamy will both be acceptable too, even though we currently view them as bad things, and while we could view this as a "slippery slope" to disaster right now, in 200 years they will be viewed as right, proper and just.
Looking at historical examples, we can see similar phenomena.
Thomas Taylor responded to Wollstonecraft's "A Vindication of the Rights of Woman" (on women's rights) by observing that "in consequence of Brutes possessing Reason, we ought to abstain from Animal Food". In the 18th century this was viewed as a joke but today many people take animal rights seriously.
Similarly, Abraham Lincoln doubtless echoed much Union (and even abolitionist) sentiment in his Fourth Debate with Stephen A. Douglas where he said that he was against the social and poltiical equality of blacks with whites. Among other things, that they should not be voters, jurors or office holders.
Yet today we find these to be uncontroversial propositions.
A more modern example: the New York Times had a good article on this, on Liberal Bioethics
The Failure of Liberal Bioethics
To summarise, there is a procedure where multiple pregnancies are 'reduced' via selective abortion (i.e. aborting one or more of the fetuses). In 1988 a prominent practitioner opposed reducing pregnancies below twins for ethical reasons, but in 2004 he endorsed it for social reasons. In 1980 when in-vitro fertilisation first became available, many feared we would have "spare" embryos being created and/or discarded, but this is precisely what we see today. There are also questions about whether aborting fetuses with Down's Syndrome amounts to eugenics, given how uncontroversial an abortion is nowadays.