I believe the answer is from Matthew 7:16 "you will know them by their fruits," so if someone claims to have the gift of discernment, but they lack love, or they don't have much compassion, then it's probably best not trusting those sort of people, but if you can tell that they are really are showing the fruit of the Holy Spirit (Love, Joy, Peace, Patience, Kindness, Goodness, Faithfulness, Gentleness, Self Control) then you can trust them.
I know it's getting harder and harder to find other Christians that you can trust, but there are still some.
For me fruits also can include results in the practical world. I think the demonic wishes to see death and destruction while the angelic wants to see life and harmony. If someone called himself a shepherd but led the sheep into danger and their lives were lost because of his incompetence, I can't see his a a competent shepherd. He could be lacking in love as you say. He could be lacking wisdom or power. He may like sheep but was too lazy to study the terrain to see where perils existed or to be able to plan ahead so they would have proper food and water. He could also be too lazy to train himself how to defend them against attack -- or too cowardly to defend them.
I believe if we love, truly love, we must seek wisdom and power also. Paul calls those faith, hope and charity -- the three go together. We are as strong as our weakest point -- and if someone is strong in one but weaker in the other two, his strength in the first will decrease unless he grows in the other two. I think Paul places importance on charity first because it's easier to start with that and increase the other two.
Someone who leads others into disaster is not hearing from God. That cannot be. While I believe in forgiving such leaders if they repent, I also think they should realize they are not fit ministers. Some of them fooled themselves. They should recognize they were guided by something other than God. People who trusted them should also see that and not allow themselves to be fooled a second time by continuing to accept failures as ministers.
Congregations are responsible for this. It is a sin to tempt to others to sin. If I knew someone had been addicted to pain pills and gotten into illegal drugs when the supply of legal pills ran out, I should not tempt him to fall again by letting pain pills in my medicine cabinet if he comes to visit. If he winds up in jail because I tempted him that way, I'm partly to blame. If a man was caught in adultery and says he's sorry, that's fine, but women should not be tempting him to repeat his offense by being alone with him, by wearing overly daring clothes, or by making gestures that could be construed as enticing. If we know the weaknesses of others and love them, we may have to adjust our own lives to avoid tempting them to sin.
What is wrong about removing failed ministers or prophets? It will hurt their feelings? If we say that, we are saying such men are motivated by pride. What is wrong about demoting someone and giving him a lesser job or perhaps no job involving trust or responsibility? In the past ten or twenty years, we have seen how poorly things turned out for the Catholic Church when they were "too easy" on offending priests. Bishops were often motivated by wanting to protect the priests rather than the congregations. It didn't work for them; and to a large extent, they have stopped trying to protect the bad apples. Protestants might learn from the mistakes of the Catholics in how to deal with failed ministers and the like.
