Wayne Grudem Discusses the importance of local churches establishing clear doctrinal boundaries, rather than downplaying the importance of theology (HT: 9Marks–original 9Marks blog post links to a longer article):
1. False teaching harms the church. Paul calls right doctrine “sound” or “healthy” (1 Tim. 1:10; 2 Tim. 4:3). False teaching, by contrast, is spiritually destructive (2 Pet. 2:1).
2. False teaching spreads. The New Testament warns us that false teaching spreads like gangrene (1 Tim. 2:17). Churches should draw boundaries for the sake of their health and even their very lives.
3. False teaching causes controversy and distracts from ministry. Paul warned Timothy to “have nothing to do with “foolish controversies” (2 Tim. 2:23; cf. Tit. 3:9). There comes a point at which it is no longer wise for a church to continue arguing over certain controversies. Clear boundaries keep a church from getting bogged down in endless quarrels and becoming distracted from its main work.
4. Jesus holds us responsible for sound doctrine. The New Testament holds church leaders—and whole churches (Gal. 1)—responsible to silence false teaching in the church (Tit. 1:10-11). Jesus rebukes churches that tolerated the presence of false teachers (Rev. 2-3), including the church at Pergamum, which merely had among them people who held to certain false teachings.