It is good to be honest, but in most cases it is not the best way. Firstly, you should make sure what people are in all situations. If they are really useless, and good for nothing, like just being badass and not helping family, doesnt do anything for it and just absorbs its budget or drives everybody mad, and you did not notice anything nice in the person, then it is good to talk about it with person. He/she may not see how bad they are, and must be told it strictly, but not offensive. Honest talk is needed.