From The Jesus You Can't Ignore by John MacArthur:
"Not every issue on which we might hold strong opinions and disagree is of primary importance. ...Anyone who is prepared to pick a fight over every minor difference of opinion is spiritually immature, sinfully belligerent - or worse. Scripture includes this clear command: "If it is possible, as much as depends onyou, live peaceably with all men" (Romans 12:18).
But sometimes - especially when a vitally important biblical truth is under assault; when the souls of people are at stake; or (above all) when the gospel message is being mangled by false teachers - sometimes, it is simply wrong to let a contrary opinion be aired without any challenge or correction. One of the worst things a believer can do is show a kind of feigned academic respect or artificial cordiality to the purveyors of serious, soul-destroying error (Psalm 129:4-8; 1 Corinthians 16:22). The notion that an amiable conversation is always superior to open conflict is quite contrary to the example Christ Himself has given us."