From your perspective it’s a generalisation, from my perspective (and the perspective of other Irish people, cos we talk to each other about it) it’s a consistent experience.
In my own experience, it’s happened when I’ve been in England (or dealing with English people for social or work situations). It’s happened more with people from Southern England, not as often with Northern English people. It’s happened most with middle-class people. It also tends to happen more with older English people who remember The Troubles. It also happens with English people who are visiting Ireland on holiday. Often, there are also comments along the lines of ‘Oh, you Irish are so [insert stereotype]’ that seem to be made with no understanding that the recipient would be upset or find it inconsiderate.
To be fair, I’ve experienced this a lot when interacting with Americans too 🤷♀️
Often, Glinner’s manner is just very Irish and I’ve found it interesting to see that some English people dislike it and see it as rude, whereas the behaviour is acceptable for Irish social norms. Ireland and England have different communication styles and, based on my experience, it would seem that this is a factor when it comes to opinions on Glinner. I’m not saying it covers (or excuses) all his interactions, it’s just something to bear in mind.