I do not know what Orange Julius thinks he is doing in this brief, weird, out-of-context moment. Donald J. Trump being offensive, mean, gross, or otherwise just exercising behavior inexcusable for others has become his norm, but he may be reenacting a bowel movement. Perhaps he is crapping all over Don Jr.'s dreams?
The odd, almost-cheering of the crowd sounds sort of like an angry mob. It is as if the people here want to see him burst a vein, or perhaps something more dramatic like exploding in a burst of pure evil.
This scene comes to mind:
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