I doubt Trump knew the symbolism of his planned white power rally in Tulsa on Juneteenth, not because I put him above such a thing, but because his brain is pudding, he knows nothing, and he wouldn't get it even if it was explained to him. But Miller knew, of course, because he watches TV shows about superheroes like the rest of us.
Likewise shifting it a day wasn't caving into goodness, it was because someone not named Miller explained that if he did it on that day it would, at this particular moment (though not any other), overshadow the coverage of Trump.