I'm not interested in delving into which repression was most egregious. Indeed, I think the argument against bigotry is harmed when we begin to put gradations on it. All bigotry and repression is bad and should be addressed for what it is, not for what it isn't by comparison to some other past transgression.

The Chinese rail workers
The Mormon Extermination Order
The treatment of Irish and Italians in NYC (at the height of US immigration)
Slavery