Why would a college Faculty hire a tutor that is a very rude person?

They act aggressive and pissed off when they have a discussion about anything with anyone and give off this bad attitude. To me, because I am a little shy, I say hello and they roll their eyes like I am a nuisance. They are very ertive I guess but surely the lecturers that put them in charge also see their bad attitude? Is it a case of a birds of a feather flock together? This tutor is also a grad student in the college but why put them in charge of anything? They will just abuse the position they have been given? Why is it that in general social life people are prone to all sorts of minimizations, rationalisations, denials about the behaviours of others. For instance, if I were to mention such rudeness to one of the lecturers they are likely to deny the tutor is like that, lie about it, deceive themselves even about the stark reality of their behaviour? Why are people like that?