Howard Roark is dismissed from the institute of technology because he is an individual who loves his work and will not compromise when genius and the integrity of his work is questioned. The faculty that feel it is their duty to expel him are threatened by the fact that he is so talented, they are probably jealous, and it drives them crazy that he will not bend to the whims of tradition and the whims of the other staff members. The group that were determined to defend him see the greatness in Roark. They see his intelligence, his drive, his quest of perfection, and his willingness to be himself despite the pressures of others or of society. It is also a matter of subjective and objective thought. The objective thinkers were defending Roark, while the mass of subjective thinkers wanted him thrown out.
I hope this helps you out.