These are grumblers, complainers, walking according to their own lusts; and they mouth great swelling words, flattering people to gain advantage. (Jude 1:16)
There is a drastic difference between constructive criticism and faultfinding. Grumblers and complainers fall into to later category. These seldom ask questions, they more often than not only question. The difference being that those who ask questions are seeking information; questioners are seeking to indict. If they do complement or affirm, they do so for the purpose of gaining an advantage. Their words of praise and acclamation are no more than flattering rhetoric. Jude clearly warns us of them. Therefore deal with grumblers and complainers as you would deal with fools. Proverbs tells us, "Answer a fool according to his folly, lest he be wise in his own eyes." Any one can succumb to the level of a fool, complaining and finding fault without a solution. Let us not be of those whom Jude spoke. Let us edify with positive reinforcements and solutions.