A sadist is having fun, is it good though?
Good and bad are relative. Subjective. Depends on your perspective.
In a conflict of any scale both parties, be it 1vs1 or alliance vs alliance fight for their own good. It’s not like one side is objectively good and another is objectively bad.
All of the mammals play games. Earning life experience, trying different survival strategies in safe conditions, determining a place in hierarchy, testing the boundaries of socially accepted behavior.
You may want to read my post Why people play, there is a segment on player motivations there.