Most U.S. companies act swiftly and forcefully to root out discrimination based on race, sex, age, or appearance when they discover it.  And there are good reasons to do so: intolerance on the job hurts morale and productivity.  It's illegal under civil-rights laws.  And offending companies can face expensive lawsuits and ruinous publicity.

But Steve Robbins, a business consultant who specializes in diversity issues, points out that not all intolerance on the job is clear-cut, easy to spot, or even conscious and deliberate. In a country in which, according to a Washington Post-ABC News poll this month, 3 in 10 Americans still admit to feelings of racial bias, prejudice can bubble up in subtle ways.

So-called harmless jokes around the office water cooler aren't so harmless to those being mocked.  And Robbins says such behavior can fester when executives and department heads ? no matter how sensitive and enlightened they may see themselves ? are part of what he calls an all-white boys' club; they can easily miss offensive innuendos or shrug them off as no big deal.

Other signs of what Robbins calls unintentional intolerance at work include high turnover among women and people of color.   He says it's a red flag when these folks get the lion's share of poor performance evaluations.  Workplace stress, lack of promotion opportunities, and what he calls flat-out exclusion can sometimes explain their inadequate productivity.

Steve Robbins notes that biases can be deeply and darkly held and are hard to change.  But companies that allow even unintented intolerance to turn into offensive behavior are asking for trouble.  Big trouble.

[Steve Robbins is the author of What If? Short Stories to Spark Diversity Dialogue, published by Davies-Black.]