Allow me to say my opinion in this matter. I,m not irish neither English so not holding any hate over past like u can say in the irish people case but....
Nazi has done many bad things still people not hate germans or look wth hate to them over the past, I think because they changed, they not anymore that people in past who hated other nations and wanted then to be the ''superior race'' . German these days changed their mentalities they are different people then was in the past ...
English people didn't changed much of their mentalities... I can see this in their comments on Fb or youtube at the Farage speech, I can see this in day by day life for 6 years living in London and Manchester, they think consider themselves above everybody else, they still hate other nations (the reason Brexit will happen) they feel proud for what their ancestors have done in past ( steeling other people lands and being racist towards others (no dogs no blacks no irish ) they still didn't changed, they have same mentality as their ancestors, the invaders. They hate.
I have been in Belfast for a tour and in one day I found my car scratched on the driver side. Thought well maybe someone who didn't care opens his/her door and scratched lightly. well... after one month I came back to Belfast and surprise, surprise I found my car scratched (this time very deep u could see the iron, no paint at all there) on the other side of my car. Now tell me would be my Dublin plates guilty for this?
Will cost me 800 sterlings to fix all this and why? because someone didn't like my car with irish plates?
In another hand, I met lovely people English ladies and English gentlemen very nice people but I can count them on my fingers, the majority I met everywhere I went have that arrogance and consider themselves superior to everybody, this things only make other people to not like them, leaving aside the history. Now I perfectly understand why Barney think and feel like this.