Judgement vs. Judgementalism

People often throw out the line, "Judge not, lest ye be judged." It's often used as a conversation stopper and only selectively applied.  Could it be that we're missing something?  The people of God are called to a discerning style of judgement, particularly in areas of doctrine and conduct.  This is not a judgemental attitude assigning value or worth or speaking of someone's eternal destiny.  Rather it is a responsibility we have to make right judgements that help us remain faithful to Christ.  It's a crucial, and needed, understanding.