So, apparently, the talking point today in some circles is that the musical Hamilton is "racist" or suspect because the creators have a very clear vision for the casting that requires all of the roles to be filled by non-white actors (the only role reserved for a white character is King George). This is, according to some, discrimination that you could never get away with if you were to try to cast only white actors.
First of all, many, many plays and musicals have very clear casting instructions, and more of those casting instructions exclude minorities (by specifying characteristics specific to Caucasians or mentioning the character's fictional biography and origin) than the reverse. Legally, casting calls have to be open to all ethnicities--but that doesn't mean all ethnicities have a real chance at a particular role It's not actually discrimination to seek to cast particular physical types to fit the vision of a character or a story.
Second of all, and more importantly--if you think this casting is about hatred of white people or any such nonsense, you've missed the point of the musical--and the reason for its popularity--entirely.
Hamilton has some specific instructions because the casting is part of the musical--the casting is meant to make these characters accessible to a modern, diverse audience, the same way the musical styles are.
Now, this has another effect, which might be uncomfortable to some--it sends the message to the dominant cultural group, who tends to assume US history belongs to them (because, honestly, it really does in many ways) that they don't own a monopoly on passion, ideals, revolution, patriotism, and so on--and that they are not the only ones who want and deserve a role in shaping the nation.
But the accessibility of seeing the founding fathers as something other than "dead white men" is of greater importance. It is challenging to inspire identification with the origins of a nation in which your ancestors were enslaved or oppressed or marginalized. But every nation needs unifying ideals and stories to tell it who it is, what it is, the US--a nation founded on ideas--needs that even more than most.
I think Lin-Manuel Miranda, as artists sometimes do, found a genius way to cut through those obstacles, and I think that the play's success can largely be attributed to this potential for unity, something many Americans crave. It does not ignore those problematic divisions at the heart of the nation's founding. It actively addresses them. But the casting emphasizes instead the common humanity of the characters and the audience.
Hamilton's casting is not meant to build barriers between us. It is about tearing the barriers between Americans down, and this is what makes it so timely.