It's funny. I could list, off the top of my head, dozens of jokes about Irish people on American network TV that are as vitriolic as what Roseanne said, but nobody gives a shit because Irish people are white, and they laugh off what is, basically, racism.
I know it's different for blacks but Irish people were historically treated like shit, too, until the 60's, and even then, the bigotry continued under Kennedy's presidency.
On the one hand I think black people should relax a little; after all slavery and segregation ended a long time ago. On the other, I think what Roseanne said was hideous but it's not really much worse than some of the stuff you see said about Irish people ; so what, is there a hierarchy of racism?
Turn on Fox News and any given day there'll be a bigoted remark about Irish (Kilmeade, Shepard Smith) but life will go on.
I also recall Kilmeade making bigoted remarks about Italians, too, but Joe Colombo isn't around anymore, so what can you do.