The English don't like anybody, but they're usually kind of passive aggressive about it.
Not true... they just know they are superior to everyone else. The English consider themselves a self-made race (which relieves God of the responsibility)
Similar scenario occured in the UK, where Irish and Scottish jokes presented the Irish and Scotts as fools and drunks, rather as those who were dominated by invading English forces.
Not sure I agree wholeheartedly. Perhaps consider both countries have a tradition of making whisky (they aren't speaking Gaelic, they're just pissed) and both had a heavy rural tradition which was not as developed as the English systems (for a number of reasons, not all connected to the English). Ironically, Scottish (lowland) education in 19th Century was way ahead of England.
Many of the Irish jokes, like the Polish jokes, come from poor, under-educated rurals coming to a new country, doing menial tasks, living in poor conditions and being unable to read or write (or speak) in the new language (if they could even read/write in their own).