When I was doing my postdoc, there was a PhD student who shared the same office with me; he didn't get along very well with me or anyone in the office. He could be described as unfriendly and a little bit rude.
As we were working on different projects, I didn't know much about his research ability.
I am now a lecturer (at the same university) and have just received funding to hire a postdoc. The same PhD student applied for the position and has since been shortlisted along with another candidate. Based on the CV alone, the PhD student is comparable to another candidate. However, based on his behaviour in the past, I don't want to consider him for the job (my department lets me make the final decision who to hire).
Is it ok to not hire someone because, from past history, I believe that we will not get along?