I kind of skimmed through, but that kind of thing was widely said and thought about Irish a long time ago both here and in Britain, both in writing and in newspaper/magazine cartoons. The Irish, being pretty powerless at the time, were extremely sensitive to it and threatened by it. Many people considered the Irish to be a different and "lower" race. Now that people of Irish ancestry are White and as well entrenched as people of any other ancestry, they mostly tolerate the drunken Irish stereotype and go along with it & live it up.
As for flag burning, I think places like car dealerships hanging flags everywhere this week and loading up their ads with flags, etc is far more insulting to the flag and those things for which it stands. At least someone who burns it sees it as a powerful symbol of something. I hate seeing it used for crass marketing.