If I've heard it once, I have heard it a thousand times. We should just love other Christians. It doesn't really matter what they believe, as long as they are sincere. It has become a truly hackneyed response by those who just don't seem to care for the truth. To them, standing for the truth is an otiose effort in light of the fact that we must love God. They just don't like loving God with their minds, though!
Jay Adams, from the Institute for Nouthetic Studies wrote a short summary of how the NT sees fighting for the truth and standing against false teaching.
I think that one of the main problems we have with people who say that we should not point out error in the teachings of others, is that they love reading the Bible devotionally, yet they never actually STUDY the Bible. Perhaps if they spend the time and effort to study the Bible, and not just treating it as a 30-day devotional script, they will start realising how important standing for the truth and against false teaching really is in the NT!