Eph 4:1 I therefore, the prisoner of the Lord, beseech you that ye walk worthy of the vocation wherewith ye are called,
4:2 With all lowliness and meekness, with longsuffering, forbearing one another in love;
Eph 4:3 Endeavouring to keep the unity of the Spirit in the bond of peace.
We mature as Christians with one purpose being unity amongst us all and with God.
Eph 4:13 Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:
In pursuing this unity will be our maturity as a Christian as we develop the positive attitudes resulting from the Love expressed towards each other that allows this unity to develop.
How can you say you love your fellow brethren in another church when they have a need you can meet and do not meet it. Or you say your denomination is better than theirs.
Gal 3:28 There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
In the eyes of God all are equal before Him and as far as God is concerned there is no difference between them in regard to race or gender. It is man who makes this division.
The people in one denomination are not superior to another. The people in one church are not superior to another. They are all equal before God. It is just what they do with the abilities which God gives them that will make them more effective spiritually and create an apparent difference.
So the Body should be working towards unity of The Spirit in the bond of the peace they have with God because of the Love they have for God and others in the body.
Satan knows this which is why we have denominations and independent churches.