Some of you might find it distasteful to make a link between the Boston bombings and Luis Suarez. But this is precisely the point, because there is indeed a link, and it highlights a difference between two different moral perspectives.

In Suarez's case, many pundits are calling for him to be banned for a long time for biting Branislav Ivanovic.This means he would get a longer ban for doing something which didn't injure his opponent than the three-game bans which are usually given for the sort of reckless tackles that can lead to serious injury. Many might think this inconsistent.

And Michael Cohen points out that Americans' responses to the Boston bombings are also inconsistent. He notes that 11 people were killed by guns on the day of the bombings alone, and that, over a year, thousands more Americans are killed by gun crime than by terrorism. And yet Americans are more willing to sacrifice freedom and money to fight terrorism than gun crime.

There's a common theme here. It's that many people are not utilitarians. Their moral sentiments are based not just upon objective costs and benefits but upon a feeling of disgust. Sure, Suarez imposed less injury upon his opponent than many reckless tackles do. But biting someone is disgusting whilst fouling them is not, and so many feel it deserves greater punishment. Similarly, terrorism evokes disgust to a greater extent than does gun crime, and so justifies a stronger policy response even though the objective costs of gun crime are greater.

This disgust has economic implications because, as Alvin Roth has described (pdf), it can prevent otherwise mutually beneficial trades such as in markets for donor organs.

In this sense, there is a direct conflict between the utilitarianism that is the default position of economists and public opinion. Many economists say "markets facilitate mutually beneficial trade, so we should have free(ish) ones in organs, drugs, prostitution etc." To which non-economists go "yuck, that's disgusting."

Herein lies a reason why, historically, utilitarianism and liberalism have tended to go together - most notably in the person of John Stuart Mill. In considering only objective costs and benefits, utilitarianism discounts disgust. It thus removes a justification for criminalizing "self-regarding" acts such as prostitution, drug-taking or (for many years) homosexuality.

And in this last word lies a problem. Over time, the things that disgust us change. Today, we find the slave trade disgusting but homosexuality not. But there was a time when the opposite was the case. Granted, there seems to be a neurological basis for the feeling of disgust - but the objects which trigger the feeling change over time.

Which raises a problem. Does this show that feelings of disgust are irrational prejudices? If so, should they have weight in policy-making? Or are they instead forms of taboo or social norms which are rationally defensible? If they are, how can utilitarians and liberals better engage with them?

I have no answers here. I'm merely pointing out that we have here two competing moral perspectives, and very often the clash between the two produces merely a sterile slanging match.

Another thing: I'm ignoring here the fact that Suarez has lengthy form and so reactions to his bite are shaped by a form of framing effect.