The thing on his head is affecting his brain

Heavens no, he is the United States President. Admittedly, he should show respect, should have stopped, stood at attention and made a joke about it after, but he doesn't act as someone lower, but as a leader who respects the leader of the country he is visiting.

That doesn't require a great deal of deference. This was a simple faux pas, an -old- news story to boot. Trump is showing a real lack of class for making a fuss about faux pas that were heavily covered in the news when it happened.