I reiterate the point made by Min and others. I've worked in an office environment back when I was in the DWP and I understand the importance of cultivating a healthy working relationship with colleagues, both on a professional and a personal level. Being given the cold shoulder for any reason is bad enough and would make the job unneccesarily harder as it is; having those childish headgames affect one's ability to do the job for which they're paid crosses the line. Personally that would be the point at which I'd bring the matter to official attention.
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'