Remember, Trump wants protests. He knows that even in a peaceful protest some fraction of "fuck-shit-up-contingent" will go around attacking people, destroying property, etc. And that gives him a justification to invoke advanced measures (Kelly, his DHS leader, specifically said that Trump had to be told multiple times he couldn't use the military on US citizens while Trump insisted that he did).

I think it's an open question at this point whether the military leadership would deny Trump's request.