You can tell people they are wrong by a look or words, but if you tell them they are wrong, do they agree with you? Never. Because via declaring them wrong, you have questioned on their intelligence and self-respect. They will strike back and will never change their minds.
So we should never begin by announcing that I am going to prove you so and so. That’s bad. If you know someone is wrong and you are going to prove that, do not let that person know, use diplomacy and do it so adroitly that no-one will know or feel about it that you are doing it.
When person makes a statement which you know is wrong, you can say that “Well, I thought otherwise, but I may be wrong which I am frequently. But let me put my thoughts on table and correct me if I am wrong”. Magic words are “I may be wrong, let me share my thoughts”. You will never get into trouble by announcing this and stop all arguments. With this way your opposition will be open-minded and listen your thoughts to discuss further. If you opposition is fair, he may also accept that he may be wrong sometimes.
Think in this way, you have very expensive paintings at your home, which you ordered by mistake. One day your friend came to your house and after seeing painting and price, he shouted “What, such an expensive painting. This is not worthy, you have been cheated”. What will you do? You will come in defensive mode and start saying that “Well, quality comes with price. These are very unique paintings that’s why expensive”. Now next day, another friend comes and he says “Wao, what a lovely paintings, I wish I could afford these”. Now your reaction will be “Honestly, I also can not afford, by mistake I ordered these”. So when we are wrong, we admit ourselves, but when someone try to prove us wrong, we never accept.
By now, you should be convinced that nothing good can be accomplished and lot of damage can be done if you tell someone straight that he is wrong. You only succeed in stripping that person’s self-dignity and making yourself an unwelcome part of any discussion.
in other words, never argue with your wife, children or others. Show respect to their opinions and do not tell them, they are wrong.