"Above all give no offense" is a noble goal for business writing--and probably an impossible one, considering how easily some people get offended. There are people who consider "Mrs." the epitome of male chauvinism, and people who claim that using "Ms." is knuckling under to radical feminism. There are people who see the quoting of a Bible verse as the first step toward a fundamentalist totalitarian state; there are people who scream "racism" if none of four experts quoted represent their ethnic group. Any blog or booklet that reaches an audience of any size will be read by someone who goes around looking for excuses to feel insulted.
However, that doesn't excuse deliberate or callous insults on a writer's part. Saying that you believe someone is mistaken is one thing; calling him an idiot or a crook is something else altogether. And there is no excuse whatsoever for writing "retard," "cripple," or any number of ethnic words long used as deliberate insults. (One list of the latter can be found at http://en.wikipedia.org/wiki/List_of_ethnic_slurs.)
For the gray areas between "everyone knows it's an insult" and "you'd have to be pretty unreasonable to make a scene over it," a few principles for coping follow. (And for insight on the issues that fuel inter-cultural clashes, visit the Cultural IQ blog.)
Wherever possible, verify the preferred term for any group referred to--the term currently preferred by the group itself, that is. Relying on what you hear secondhand or on what was standard thirty years ago can get you in trouble; even within groups, "acceptable" words change from decade to decade. The term your father's gardener thought nothing of may be anathema to his granddaughter.
Avoid all idioms that mention groups by name; most such are now considered stereotyping. It's not worth the risk.
Never, under any circumstances, contradict someone who is in a better position to know than you are. A surprising number of bloggers presume to "correct" an Ecuadorian diplomat on what country is southeast of Ecuador (without bothering to check the map, of course) or a seminary professor on what books are or aren't in the Bible.
Avoid contradicting anyone at all unless the wrong information could have significant consequences--and even then, be low-key and respectful. Correcting people just to show off your superior knowledge, or with words that imply "how can you be so stupid?," only says to others that you are too arrogant to work with.
Finally, for those times when someone expresses offense despite your best efforts, seriously consider that you may owe an apology--and be willing to deliver it, publicly if necessary, without argument or excuse. Genuine humility is so rare that it can only help your reputation. Even if your conscience or understanding of the facts won't let you go as far as "you were right, I was wrong," be willing to acknowledge the merits of your opponent's position. In those rare cases where there are none (the fanatic who insists that everyone who refuses to agree the earth will blow up next week is a tool of Satan), better to ignore it altogether than to argue, which only encourages your opponent and makes you look petty.
Perhaps an even better principle than "above all give no offense" is "above all, never imply you're incapable of a mistake." Where the facts support you, let them speak for themselves.