Why are people so sensitive to racism?

I recently asked a question wondering why african-americans continue to live in this country when we were the ones who enslaved them and were racist towards them. I got many intellegent answers explaining how for generations they couldn't leave, they didn't want to leave, ext. while others simply accused me of being an "inbread racist" and a "horrible person". I was just wondering why people "hate on me" so much and why my question was deleted.