You've got to know when to hold 'em, know when to fold 'em, and know when to run.
(Kenny Rogers, The Gambler)
The problem with the Zen philosophy of always aiming for peace, wisdom and harmony is that it is taken from a spiritual plane that is only present one step at a time in our spiritual development. We progress along a spiral, higher and higher. Some turmoil along the Way may be necessary to get ready for the next spiritual dimension.
Mind though, there is never ever a time to lash out at your brother, for if you lash out at him, you will only injure yourself. But sometimes he invites you to give him a lesson; just do your job without getting emotionally involved. Your spiritual super-ego will probably scream murder but just get the job done. If your intention is whole, you will not accumulate any karmic baggage, just as he stands to benefit from your little push.
If this all sounds complicated, stop thinking and just do what you feel you have to do. Durga Maa will make everything apparent to you. Life is a dance, drop your worries and do your thing. She will dance with you every step of the Way!