Poor whites and the race factor

I wondered for a while why there was/is so much hatred of blacks among people of Irish heritage and poor whites in general. Beyond observation of current events, it seems to come up again and again in history (even in my informal, non-exhaustive studies) that you see especially high levels of racism among poor whites and Irish immigrants in particular(who tended to be uneducated, discriminated against, and thus very poor).

I concluded that in a highly hierarchical society such as the Old South, those who are near/at the bottom of the totem pole can be expected to fight hard for any status that they have. When all of a sudden the stratus below you starts organizing effectively for more civil rights and equality (leaving you behind), you can't be expected to be happy about your impending loss of relative status. This is obviously not the entire explanation, but I think it is partially what was/is going on.

Anyway, here's an article I stumbled upon that articulates very well what I concluded (wow that sounds really snotty).

The Root: The Birthers and Jim Crow 2.0

Update: Another article that talks about the issue well as far as I can tell.

racismview.com : Irish-Americans, Racism and the Pursuit of Whiteness