Consideration of silence

Kindness is cruel. Not to say is not so sweet. There is sometimes the case that the one needs to be told something bad. However I know that there are people who consider that not to say something for a mistaking man is kind. I can't believe that. Is this a Japanese culture? Do you think to be silent is smart? People say silence is gold. But I think it is an excuse of weak. The weak means the one who cannot explain himself optimally. We had better help the one who is mistaking.