Repentance is about turning from our wrong thinking to that of Christ Jesus. We must understand and accept His ways. He never changes.
Preaching the Gospel of Grace Through Faith in Jesus Christ brings a believer to repentance and acceptance of His standards and authority as the basis for their life.
Any person not in agreement with Jesus is not born of His Holy Spirit and so, is ineligible for His presence, which is heaven.
Fellowship requires agreement. Evil does not compromise as compromise requires good will. Hence, when we try to fellowship with evil, we must do the compromising.
The Lord Jesus Christ is inclusive only on His terms. He accepts no one who has not believed on Him and been born of His Holy Spirit.
The reason for this rigidity is that light and darkness cannot coexist. Neither can good and evil,
We see from just the two verses above that External Peace is impossible when there is division at the spiritual level.
Holiness is a byproduct of being In Christ. It is a mindset of light enabling good vision, clear thinking, right choices and clean living.
So, peace is expected between fellow believers because of the Holy Spirit who unifies us in love.
But peace between a believer and non-believer must be pursued as it is difficult to hang on to.