6. Puckered chin

Some of Trump’s zipped smiles are straightforward, but a large proportion of them are accompanied by a puckeredchin. These are what psychologists call “blended facial expressions”. The presence of this additional facial expression is quite significant because people often pull their chins in when they feel threatened – it’s a way of tensing the chin in anticipation of being symbolically punched in the face. The fact that a puckered chin features in so many of Trump’s zipped smiles suggests that he frequently feels threatened. Because zipped smiles are so effective at capturing people’s attention, they provide a perfect vehicle for Trump to disguise his feelings of vulnerability. All this is likely to be entirely unconscious, but by unwittingly externalising his feelings in this way Trump proves that he is not as tough as he would like everyone to think.

https://www.theguardian.com/us-news/2017/jan/15/the-seven-faces-of-donald-trump-a-psychologists-view

I wonder if he knows on some level how much he is hated, but he just won't let that fact rise to the forefront of his consciousness.