Since I'm more or less bound to a professional code of ethics at this point, honesty is actually a requirement for me; exaggeration is frowned upon as well, at least concerning my own abilities. Having to disclose potential conflicts of interest upfront is another requirement, even if I have no intention of being dishonest. And seeing that my chosen career path is in structural engineering, and there's no room for neglecting potential errors in design or construction; any lies, especially lies by omission, can have fatal consequences. So yes, lying isn't really allowed; it may not be illegal to do so, but loss of my liscence to practice and reputation are just as significant.
I also happen to have a strong aversion to lying as well, and will avoid doing so as much as possible. If in position where telling the truth is harmful, I would probably explicitly refuse to tell or remain quiet (effectively a "lie by omission"); this is assuming the truth in particular is not something which needs to be said, but if not it will be said.
That being said, I can understand there are a handful of situations where being dishonest could be the ideal course of action; however, those generally involve dealing with individuals who aren't willing to be reasonable nor understanding. To avert a more serious and harmful problem, due to the person taking a certain course of action due to an emotional decision, lying to them may be acceptable. One should loathe having to resort to that course of action, and it should only be used with absolutely necessary; furthermore it is to help them, not yourself.
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The difficulty for me will be trying to be tactful and not callous, especially dealing with those who are being... "abrasive". Maintaining professional conduct & appearances is another requirement, but thankfully it doesn't take precedence over the other necessities (safety, competence, honesty); still, there are a few cases where it's very difficult to be respectful of others (particularly when they aren't extending the same courtesy).
As tempting as it can be and how much the troublesome individual may deserve it, sarcasm and passive-aggressive statements aren't the way to go.
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As for those who see no issue in lying... well, I suppose it's a case of "ignorance is bliss". Possibly due to not being a position of high responsibility, where the reprecussions for being dishonest do not go beyond your own state of affairs. I suppose one could be envious of their ability to disregard the impact of their actions on others, for professionals have no such luxury.
