We've all had to deal with difficult people at work. It doesn't get easier when the difficult people are those you serve.
My director once shared his thoughts on a particular audience and it has stuck with me. In higher ed, some of those served are faculty members that have made their living questioning the world around them in research. This same perspective very likely is what elevated these folks above their peers and afforded them opportunities.
Looking at this group in this light, it's no suprise that they are labeled as critical or difficult to work with. Some do not have the ability to just turn this skill off. Why should we expect any less from them?
I believe we can become more patient (or tolerant) of those we serve if we better understand them. Do your best to find some way to add value in difficult circumstances.