Once upon a time in the 1970s, the economist Arthur Laffer was having lunch with Dick Cheney and Donald Rumsfeld. He drew a plot of government tax revenue versus the income-tax rate in which he set revenue at zero at both zero percent and one-hundred percent. From this, he argued that the government may get more income at a lower tax rate than it would at a higher one. Ever since, Republican politicians have gestured vaguely at the Laffer curve when claiming that their tax cuts will somehow help pay off the national debt. Such tax cuts have, universally, not.
In 1945, the philosopher Karl Popper wrote “Less well known is the paradox of tolerance: Unlimited tolerance must lead to the disappearance of tolerance.” Ever since then, people on the left have gestured vaguely at the paradox of tolerance to defend their ‘no platform’ policies or justify their anger at the ACLU for defending people they dislike.
The Laffer curve and the paradox of tolerance both set out to do something valuable: they give reason to think that some seemingly obvious piece of common sense wisdom may not be true. The Laffer curve challenges the idea that increasing tax rates must always result in increased tax revenue, while the paradox of tolerance shows a potential problem with the idea that extending tolerance more widely must always lead to a more tolerant society.
They both rely on seemingly common-sense assumptions that are themselves subject to doubt. Laffer assumed that with a one-hundred percent tax rate there could be no incentive to work and thus there would be no income to tax. While this may be true of some systems, one can imagine plausible systems where it isn't; a system with a one-hundred percent income tax and a universal basic income that grants money above and beyond the basic income to workers in proportion with the value of their work to the national economy would create a rather straightforward incentive. The relevance of a model using a single tax rate to a progressive system of several taxes is also doubtful.
Popper assumes that tolerance for the intolerant will cause them to gain power with which they will put an end to tolerance. This is possible, but by no means certain. it is entirely possible that in societies where secular-rationalist and self-expression values predominate intolerance will simply be unable to gain popularity. If this is the case, then the most powerful tools for securing tolerance are those that ensure individual safety and freedom from want as well as self-determination and functioning democracy. It can also be the case that laws aimed against intolerance can create intolerance themselves, as has happened when the existence of hate speech laws is used to argue for blasphemy laws.
Nevertheless, let us grant Laffer and Popper both the far ends of their respective curves. if we accept their arguments, what courses of action does this justify? Few, if any, on their own. The existence of some income-tax rate higher than which tax takes begin to fall does not tell you what that rate is nor does it justify any specific tax cut proposal unless the current rate already is one-hundred percent and the tax take is zero. The Laffer curve, at best, tells you that you should actively consider the idea that the tax rate may be too high and search for other evidence that might support the theory.
Similarly, Popper's paradox of tolerance does not in itself support any particular measure to combat intolerance. It cannot, on its own, be invoked to support a hate speech law, a ‘no platform’ policy, or punching some random person you happen to disagree with in the face. Popper himself never intended it as a blanket support for all laws someone might propose to suppress intolerant ideas; his famous quote continues, “In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be unwise. But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant.”
Popper's full explanation makes the point a bit more clear: if you accept his paradox it simply suggests that there are some circumstances where refusal to tolerate the intolerant may increase tolerance. He gives some reasonable conditions: when the intolerant exempt themselves from rational discourse or enforce their intolerant beliefs with violence. I'm in complete support of a refusal to tolerate violent expressions of an ideology, though this does not ‘taint’ the ideology; people may have a legitimate grievance and be driven to the point of unreasoning fury when society does ill to them. We can forbid the violence, but the actions of the aggrieved in no way lessen the legitimacy of a grievance.
Refusing to tolerate those who exempt themselves from rational discourse is more fraught. There is a moral hazard in making it advantageous to caricature ones opponents as irrational, and doing so is really quite popular. I do not agree with the linked articles; I use them to show that seldom will ones opponents do one the favor of claiming that reason is a dangerous beast that one must guard oneself against. Modern society rightly gives prestige to reason and science (even if it doesn't do as good a job of teaching people what those things are as I wold like) and most ideologies will try to claim their imprimatur whether they deserve it or not. Getting everyone to agree on which groups are impervious to reason may be non-trivial.
There are also ways a society can refuse to tolerate the intolerant besides restricting speech, and, if the general failure of Europe's hate-speech laws to make Europe less prone to bigotry is any sign, much more effective ones. A constitution or a charter of rights and freedoms that creates a much higher burden for any group wanting to enact certain kinds of laws is (when written properly) effectively a bulwark against intolerance as it puts intolerant laws at a severe disadvantage in the legislative and judicial spheres. Anti-discrimination laws restrict the harm that the intolerant can do in law and commerce. Social actions beyond the law can also have a positive impact; community norms against intolerance and a policy of actively showing respect for and supporting minorities can go a counter the emboldening belief intolerant groups hold that they represent a silent majority.
It may well be the case that restrictions on speech are beneficial and necessary. I tend to think that content-neutral laws against harassment will be more effective in general against all kinds of intolerance than specific laws against hate speech, attempts to blacklist people who say objectionable things, or ‘no platform’ policies, but I may be wrong. If I am wrong, there should be evidence to demonstrate the fact, not merely a sufficiently objectionable target. Any policy that claims to fight intolerance must earn its keep by providing sufficient reason to believe that it will both be effective in its stated goal and not bring about enough negative side effects to counter what good it does. Otherwise, it will have as much legitimacy as the latest attempt to pay off the Federal debt by cutting taxes on the one percent.