In their frustration they may direct their hostility at the contractors who are replacing their former co-workers. Another reason permanent employees may show resentment toward contractors is the tremendous freedom contractors have to do their job without the constant distractions of stupid corporate busy work, interminable meetings, and pressure from above. Employees are often envious of contractors, and of the perception that contractors make more money with less stress. There is real resentment directed at everyone, including you. Corporations are increasingly undergoing downsizing, reorganization, acquisition, and merger.
Projects come, and projects go.
Change can be very disquieting to permanent employees. As an outsider and a short-timer, you make a convenient target for their frustrations. Some people are simply rude, and you perceive it as resentment directed at you. I occasionally meet managers who are arrogant toward everyone. Others are operating so far above their level of competence that they are extremely defensive about their intellectual and professional impotence.