Selfishness and fraternity are opposites?

In terms of public values, yes. But in fact, the two often go hand in hand. For example, in love, you can tolerate each other's shortcomings, but you don't like each other fighting with other members of the opposite sex.

Selfishness and fraternity should have limits. When there is a conflict, we should choose the best one to deal with it.

You can take both, so I don't think they are opposite. Selfishness and fraternity do not have certain antonyms.