They must be silenced, because they are ruining whole households by teaching things they ought not to teach - and that for the sake of dishonest gain.
Review the previous 10 verses before moving on to this next one.
This verses warns about the danger of false teachers, as do many other verses in Bible. False teachers are so dangerous because their teachings attack the foundation of truth and integrity upon which the Christian faith is built. We need to be able to recognize false teaching and stay away from it.
LeRoy Eims on the importance of Scripture memory: "I think two of the master strokes of the devil have been to convince people he doesn't exist, and that Scripture memory is only for children. He remembers the humility of defeat when Jesus Christ, who was tempted in all points like as we are, met him with the Word of God." (What Every Christian Should Know About Growing; p. 26-27)