Some people with difficult attitudes appear to be unimportant in the scheme of things, and you might be tempted to ignore them. However, just because someone lacks the social or professional skills to get along with other doesn't mean that they can't take a positive contribution to your department - a contribution that might even further your career.
As a manager or co-worker, you might have a great deal to gain from making an extra effort to approach, talk to, and come to build a positive working relationship with a person everyone else has labeled "difficult." Sometimes people with difficult personalities are exceptionally intelligent or gifted with numbers. Sometimes they're innovative and good at thinking outside the box. Or they might be instinctive, analytical problem solvers - if only someone would ask. If you turn a blind eye to these folks, you might be losing a lot.