A lot of people, even people who are quite morally rigorous, assent in practice to the norm that an off-color joke being hilarious can make it acceptable. I cannot emphasize enough that, in my experience, even people one would think are morally rigid seem in many cases to give at least tacit consent to this principle.
Of course, how blue or off-color a joke can be before no amount of laughs can save it is a matter of dispute. Also, not everyone agrees with this principle. This makes sense because prima facie there’s really no good reason that being funny should redeem a joke if it’s unethical. Still, the view has purchase even in surprising places.
The sociological explanation for why funniness can rescue jokes and their makers seems like it’s probably going to be something simple like:
Saying disgraceful things is low status, but saying funny things is high status, and they sort of ‘cancel out’.
But I’m interested in whether there’s any valid or at least compelling defense of this principle.
The simplest defense might be called the ‘enough value’ defense- it’s good to let really funny jokes go, because the comedian has produced enough extra value to cancel out the harm. Thus the joke is an overall positive, and we wouldn’t want to discourage overall positives. One version of this suggested to me by a philosopher is that the value is aesthetic rather than moral, but one might also attribute it to the ethical benefits of laughter, which most of us think makes life better.
You might combine the extra value defense with a self-limiting argument: if unfunny and immoral jokes are allowed, people will just use that as an opportunity to do bad things at will. However, if only good jokes get an exemption, since good jokes are rare, a norm that grants such an exemption has a nice self-limiting feature.
Another theory I call the ‘net benefits to the victims’ view goes as follows. Unethical and ethically dubious jokes are generally considered as such because it is thought (rightly or wrongly depending on the joke) that they may harm people- a stereotyped group, an individual who is a target of ribbing, etc. If a joke is good enough to make the people it’s about laugh, then it’s less likely to do them any kind of net harm. Hence it has no (net) victims. Thus it is ‘defused’ in a sense.
One worry you might have about this is that targeted jokes that ‘go down smoothly’ even for their ‘targets’ are actually worse because they get past a person’s defenses and more directly affect their self-image. When I raised this, the response was that it’s paternalistic to tell people they can’t forgive a joke about themselves because it’s funny- that’s up to them.
A more pragmatic spin on a similar ‘no-objectors’ theme goes like this- the reason people tend to get away with really good jokes is that everyone present laughs. This means they lack the moral high ground to speak up against the joke. In general morality often has a a ‘civil law’ flavor: if no one has standing, there’s no case.
I find myself wondering how all this relates to the cultural archetype of the trickster. A figure whose exceptional cleverness allows them to move within, beyond and between social norms- and who is often portrayed as telling jokes and playing pranks that are taboo- but generally getting away with them due to their exceptional wit. Anansi, Coyote, Loki, Māui and scores of scores more. The trope is also present in contemporary fiction- e.g. Tyrion Lannister
Our culture tends to regard humor as generally permissible unless something is defective with it, but many other cultures have taken a much harder line on comedy- seeing it as suspect in general, or even forbidden in all or most cases. I join many others in wondering whether groups that cracked down hard on comedy - e.g. the puritans- did it out of fear that comedy provided a path to ‘safe’ transgression of their hard- yet brittle- rules. The comical suspension of the ethical has threatened many. Some of them deserved threatening, others among them did not.
Edit: JQXVN makes a valuable point in the comments: The value of the joke isn't just redemptive, it's evidence that the joke-maker made the joke for reasons other than the bad ones we're likely concerned about. If you create or repeat a funny off-color joke, you may or may not have done so to advance the inherent humor of it, but if you create or repeat a terrible off-color joke, all that you can be advancing are the twisted values that make the joke off-color.
Downsides
I don’t want to suggest abolishing the funny-enough rule for many reasons. I think that in general we overestimate the harms of ethically dubious humor relative to more material harms and would prefer we focused on those. I also think that if this were the sort of principle that could be abolished, it would have been abolished long ago given how much different groups, for different reasons, have hated different kinds of taboo humor. That said, the rule of funny enough has a few perverse effects worth noting:
Leniency for hilarious but off-color jokes contains a built-in motivation for these jokes. The comedian wants to test themselves- to see what the most outrageous thing they can get away with saying because it’s funny enough is.
Also, not to be ‘that guy’ but as a rule it’s inherently prejudiced against the neurodivergent, non-native speakers of the language, people from outside the social class of their listeners etc.- in other words, people who will tend to have more trouble gauging whether a joke will be funny enough to the audience to be ‘gotten away with’.
It’s also worth noting that people are filthy hypocrites about this sort of thing. At the moment one half of the people interested in politics are screaming out “why can’t people take a joke anymore”. Yet after Trump talked about bombing 52 Iranian cultural sites, Asheen Phansey responded with the quip that perhaps Iran should make a similar list of American cultural sites to deter America. The very same people who whine about how PC culture means we can’t make jokes anymore got Phansey fired. Often, when people profess to be forgiving of ‘taboo humor’ they just mean humor that for them, is not all that taboo.
I don’t have the answers, but I think your best bet is trying to be kind, gentle, and a repairer of the world. Exactly what this implies on the question of off-color jokes, I’m not sure, but I think you’ll figure it out in practice, more so than in theory. Be as cunning as bears and as kind as Labradors.
The value of the joke isn't just redemptive, it's evidence that the joke-maker made the joke for reasons other than the bad ones we're likely concerned about. If you create or repeat a funny off-color joke, you may or may not have done so to advance the inherent humor of it, but if you create or repeat a terrible off-color joke, all that you can be advancing are the twisted values that make the joke off-color.
May I suggest an additional type of humor for inclusion in your discussion: Monty Python’s goal of being so funny that no one dares laugh.