The poet presents two contrasting facets of the same character: samḥun mukhālaqatī (easy dealings) and ẓulmī bāsilun (severe retaliation). Each is placed within an idhā condition.
CircumstancePoet’s claimWithout injusticeOpen, pleasant behaviourWhen wrongedA harsh, bitter response
This is poetic contrast, not an unrestricted justification for violence.