The subject of preconceived (typically unfavorable) notions about a group of people in society is explored.

Notes:
The themes "hatred in society" or "ethnic hatred" are more appropriate in cases where there is hostility but not necessarily any preconceived notions. A people at war may, for example, quite logically hate their enemy on account of that enemy being demonstrably organized to do murder.

References:
https://en.wikipedia.org/wiki/Prejudice