Some who have been persuaded by the heretics appear to be combative and they must be approached with caution. The fear which Jude has in mind likely refers to temptation. The church should show mercy but recognize the temptations that could befall them as they seek to do so (see Galatians 6:1).1
23 save others by snatching them out of the fire; to others show mercy with fear, hating even the garment stained by the flesh.