The New Testament charges congregations with resolving disputes between fellow believers. See, for instance, Matthew 18 and 1 Corinthians 6:1-8. Since it glorifies Christ, unity within the body should be a goal of all members. See, for instance, John 17 and Philippians 1:27-2:11.
Since most New Testament letters are addressed to congregations (rather than individuals or groups within congregations), we view congregations as responsible for their members' doctrine and practice.
As 1 Peter 2 indicates, God calls His people to glorify Him by living in accordance with their identity in Christ Jesus. His people are, of course, sinners saved by His grace in whom His Spirit now resides, transforming them into His likeness. Members of local congregations should therefore seek to live in a manner worthy of their calling in Christ (per Ephesians 4:1-6 and Philippians 1:27-30), thus testifying to His saving work in their lives (per Philippians 1:28).
Meaningful church membership occurs in a context in which this mandate is both appreciated and pursued. As we understand Scripture, no Christian is an island; God works in and through the community of His people—which is, of course, the church—to accomplish His purposes within our lives. Church membership should thus not be entered into lightly; congregations have a mandate from Christ to hold their members accountable to biblical standards of belief and practice.
Moreover, the command to love one another permeates the New Testament. As a community of believers, we therefore strive to live in unity with one another, sacrificing our own interests and preferences for the community's sake. We pray our congregation will become known for the love we show to all those with whom we have contact.
May the Lord be glorified by the life of His bride, the church!