Roberts To Play Tubman?

Silly stories say that a movie exec once suggested that Julia Roberts play Harriet Tubman in film, which, of course, makes no sense, as Harriet clearly would have wrapped her hair and not had access to 21st century dentistry, and Roberts relying heavily on both hair and teeth in all of her roles. And,  there was also the race thing. But why? "Hamilton" is a HUGE hit on Broadway and throughout the country.
       

Pretty certain that, historically, our Founders did not look quite like the above pic....So why would Tubman be off-limits? The Norse deity Brunnhilde the Valkyrie, who was portrayed for decades in Marvel comics as:
    

             blonde and Nordic. But she is portrayed in Marvel MOVIES as:

Brownhilde, Tessa Thompson. No cries of "Appropriation!" except from maybe diehard fans of the comics and/or mythology.
  So why is Tubman so triggering? Well, she was a real person, but so was Hamilton. She is set to replace Andrew Jackson on the $20 bill, and Hamilton will continue to be portrayed on the $10 note. It's similar to the way we look at being gay in the current culture. The closet door only swings one way. You can come out,m and it is celebrated. But going IN is looked at askance. There are questions of "conversion" and "confusion". Race-blind casting was considered a progressive means of bringing "representation" to media. When there was no indication as to a character's racial identity, casting agents were directed to ask "well, why couldn't he/she be....?", and that eventually became a quota system whereby every vehicle must have a certain amount of representation or the lack of it must be defended. And now we have just outright replacement, but it must NEVER be a white actor or actress playing a non-white role, because THAT would be "wrong". And no one wants to be wrong.