I bet the play was a good way to get a sense of the suffering on a slave ship, in a way that other historical venues are, eg Valley Forge on a -10 day, the Holocaust Museum, etc.
That said, slavery was 150 years ago. Anyone that allows that to enter their conscious and let it affect how they approach the next hour, day or year in how to make their personal life better is wasting their time. It bears no impact, and wishing it so takes one off track.
I know people who actually engage in freeing women from slave masters throughout the Washington DC area (mostly citizens of the Philippines or Indonesia brought here as unpaid house servants).
What do you mean that it's 150 years ago?