The issue of sensitivity varies from one person to another. Apparently, we have people that are extremely sensitive to offence, and this could make them to be highly irritable. While on the other hand, there are those theirs are not too that serious. And interestingly, the level of one's sensitivity is directly proportional to the degree of how they react to offence. Sadly, for some of those their sensitivity is extreme, they find it very hard to get over hurts. And I guess that's the category your colleague at work falls.
The honest truth is, I am a very sensitive type of person. Little things usually get to me if they are things that show no respect for my feelings. Most times, I feel easily irritated when someone close to me is forming to be too busy for me. I see it as if they are perceiving me as a burden to them, and this could make me to withdraw completely from them and if care is not taken, they might never get to hear from me again, maybe until they try to reach out to me. But my kind of sensitivity is the type that easily let go of hurt. I forgive very easily without keeping grudges or malice.
Basically, most people that are sensitive like me get easily offended, because they like to treat others the way they would like to be treated. And if they feel you are not doing so, they would rather become resentful of you or they would simply work away.
But for those that their sensitivity is all about getting angry easily and keeping malice unnecessarily, I think they are not wise because they are only destroying their relationship, which could deprive them of the benefits it offers. They are only burning bridges through their insensitive actions.