I'm sure you're right in your observation, supra. I'm not so sure that we frail human creatures are always so good at identifying which is true and which is false. For instance, I'm reminded of the parable of the wheat and the tares. As well as the sourcerer who was casting out spells "in Jesus' name; without looking it up, Jesus' response was something along the lines of "He who is not against us is for us." Not to mention the parable of the sower, which tells us that it is our job to cast out the good seed, but that the harvest is the responsibility of God.
All things considered, I believe I would rather do and say things that tend to build up the body of Christ, even if an occasional false "tare" is roped in, than to do anything that would tend to tear down the body of Christ for fear that I would chase the wrong person away.
Peace.