I've boldened a part of BD's post. It seems she is wondering the same thing I did.
When I read the OP's description of the incident, the first thing I thought was......well what kind of a dig was that? Was that directed at her in a "non immigrant" kind of way?
This is one of those things that intrigues me. Because just taken at face value you have a slightly grumpy guy voicing his concerns about convention; manners and rules are important or we slide into chaos. The development of manners and convention in GB is fascinating. It mingles class with supply and demand and economics and all kinds of things.
Manners, like accents and grammar, are a way of separating people into categories. Historically the type of hat you wore designated your class - even the angle at which you wore it. Wigs were worn, yes, as a way to combat head lice, but more so to divide, as they cost more than a worker made in a year. Dances were not held for people to "shake their groove things" but were intricate tests of training. The shape of your head apparently was (and to some still is sort of) an indicator of your nature - the long "lion-like" faces of the aristocracy v. the round "jug-eared" appearance of a Welsh miner. It is interesting, when you think that perhaps this sort of thing has been banished, to consider that weight is now becoming the same sort of wedge issue.
Now plop an immigrant into the mix. Where do they fit in? They know you are North American or something. Why are you here? What are your intentions? Are you a dishwasher, or like Oprah are you rich enough to buy the whole shop 1000 times over? You defy easy generalisation and render useless all of those easy historical systems for separating and defining.
This, I think, is one of the strongest drivers behind anti immigrant feelings in the UK. Aside from the natural fear of the unknown, of change (risk) - immigrants defy categorisation and shake the foundations of the internal self-defining structures individuals build up to mentally secure personal status.
