The Jews, Irish and WASPs ruled Boston for years. Back in the 50's the blacks started moving into the Blue Hill ave corridor from Roxbury, to Dorchester and to Mattapan. That was made possible when the banks got together with the Boston elite and redlined the older Jewish neighborhoods and gave loans at good rates to black families. The thought being that the Jews would be taken out as a political force. (More racism/anti semitism)
The Irish and Italians had a rivalry but when you look at the battle for Dorchester and Southie it was all about the Irish and the blacks.
As an aside, before the poverty programs put forth by the democrats the Irish and blacks had a pretty similar place in life which explains the rivalry in some ways. Both were looked down upon and discriminated against. Irish were looked upon as being worth less than slaves. But, both had a stong tie in to family and the church.
I guess you're way before my time if you recall the Jews being a major political force in Boston.
Are you on drugs?