The biggest motivation is to increase viewership while supporting a certain candidate and promoting him. Privately owned media sources are usually biased towards someone and help them while they show bad things about other candidates. In return, they expect support from the candidate if they ever get into a position of power. By being controversial, they get new viewers and earn more money.
The answer is Civil Rights Act of 1964, which barred discrimination on race, color, religion, national origin and sex.
