Are gossiping, stereotyping, or snobbery ever appropriate? Depends.

Such blanket condemnations, according to Emrys Westacott, a professor of philosophy at Alfred University, paper over complexities. In “The Virtues of Our Vices,’’ Westacott asks tough questions about the nature and meaning of these “bad habits.’’ Arguing that conventional wisdom masks the benefits of practices often viewed as moral failings, he challenges us to engage “with a world in which categories, terminologies, expectations, and norms are in constant flux.’’ His book is accessible, rigorous, and droll. Although not always persuasive, it is a practical primer on how to think about ethics in everyday life.

With cultural norms, Westacott demonstrates, “[a]n exact fit between definition and the thing being defined’’ is virtually unattainable. He acknowledges, for example, that stereotyping is often harmful and that calling someone a snob can be a useful reminder that democratic societies determine the worth of people not by their social status but by their merit. And yet, he points out, even when snobbery is defined with precision as a belief “without sufficient justification that you are superior to another person in certain respects because you belong to or are associated with some group that you think places you above them in the social hierarchy,’’ our response to it depends on whether the comment occurs in a social context in which the snob is degrading a person’s life, happiness, and experience and has “an oppressive function and power.’’ For this reason, we view snobbish comments directed at African-Americans or “red necks’’ differently from those directed at Norwegians.

Westacott complicates the problem further with a reminder that we make “probability-based generalizations’’ all the time, many of which are accurate. Judges, after all, do tend to know more about the law than jurors; Californians may well be more laid-back than New Yorkers. Snobbery about things (Florence is a more interesting city than Fargo; hip-hop isn’t music), Westacott insists, can be acceptable, edifying, and even charming conversational gambits if - and that’s a big if - the criteria for the judgments are specified (chess takes more skill than dominoes), and preference is decoupled from prejudice.

In a provocative and unsettling challenge to toleration, a sacred cow of modern, liberal societies, Westcott goes even further. We need not respect beliefs that many people consider important, he claims, including religious beliefs that are “incompatible with a naturalistic, scientifically informed outlook.’’ A person who announces that gay men will burn in hell for eternity, he indicates, deserves to be condemned as bigoted and cruel. Someone who is certain that the Holocaust never happened or that President Obama wasn’t born here ought to be dismissed as ignorant and hateful.

Less clear in “The Virtues of Our Vices’’ is Westacott’s view of the appropriate - and permissible - behavioral response to baseless and offensive opinions. Can a supervisor rule out a job applicant who wants to postpone an interview because it is scheduled for the seventh of the month, his unlucky number? How about an orthodox Jew who refuses to travel on the Sabbath? Or an individual who deems some sexual relationships between children and adults as mutually beneficial and wants to work at a day-care center? Should it matter that the belief in question is part of a traditional, widely respected metaphysical system? And, most importantly, can we find a way to praise (and practice) free speech and nourish diverse (and even unpopular) beliefs without sacrificing intellectual rigor and succumbing to a mindless and destructive relativism?

Despite his virtues as a logician, linguist, and moral philosopher, which are considerable, Westacott’s defense of his virtues is less than air tight. Gossip, he points out, can provide useful information, correct false impressions, counteract secrecy, and foster intimacy and ethical reflection. However, as Westacott acknowledges, when gossip is distorted, false or malicious, as it often is, it harms individuals, slanders groups, and debases our culture. And, although some of us should lighten up, it’s a stretch to suggest that, in some ways, sick jokes constitute evidence that, by rejecting traditional taboos, the culture “is healthy, just as our anxieties about rudeness may be a symptom of cultural dynamism.’’

At bottom, though, Westacott is right. There is no clear cut, algorithmic formula to determine when (or whether) each of these “bad habits’’ is morally acceptable. We can (and must) combine reason with “phronesis - practical wisdom - factoring in and weighing up all sorts of variables.’’

And, I would add, we should summon up the courage (which is what it will take) to withhold attention and respect from colleagues, friends, and family members when they are destructively rude, snobbish, gossipy, jokey, and opinionated.

Glenn C. Altschuler is the Thomas and Dorothy Litwin Professor of American Studies at Cornell University.