Who was more hated in 1870 Irish polish or blacks ?

By the English. Probably the Irish.

It depends on where you are asking about. And what you mean by hated. For instance blacks in the American south were as a rule considered inferior by whites but were not hated. In the Northeast there was sometimes hate between various ethnic groups. For the most part it was less a matter of hate than of social status.

Polish is one of those words which absolutely demands a capital letter if you want to make your question clear. A comma would help too.

Blacks. It was just after the war, and the plantation owners were pitting black against white.

Irish came in a close second though.

Depends on WHERE dumbass. It's a big world.