It depends on what you mean by "show". If it means that a man does not get emotional about something, then it is false. I, for one, am an emotional guy. I have very deep emotions. However, if you say that a man does not express emotions on his face, it may be true. I very rarely allow my expressions to show up on my face. Not because it is not manly, but simply because others don't have a business knowing my emotions.