It really could just be a case of being six. Sometimes the world gets more complex and more overwhelming, a combination of personal development (maybe he started to get have more cognitive understanding of other people's emotions and general situations, but not yet the emotional regulation to deal with that), and being in a more demanding external environment (6yos are supposed to sit still and pay attention most of the time in school, whereas 5yos can probably move around more and play more, and that transition might be hard for an autistic kid.) I doubt that at 6 he is paying attention to the way the media talks about Trump and has concluded that he, as a Man, has a licence to harm other people for fun.

None of which is to say that smashing things, throwing things at another kid, or using graphic violent threats are acceptable behaviours. But I feel it's worth entertaining the possibility that these bad behaviours are expressions of overwhelm, rather than intentional malice.