It would short circuit a lot of repetition if you would read what has been written. The Backstop was originally agreed to stop a physical hard border infrastructure on the island of Ireland. It had no relevance to a hard border at Calais.
Without a Deal it is inevitable that there will be a physical border on the Newry Dundalk road,to stop traffic in goods. Not to stop traffic in people. There are already agreements in place,as far back as 1923, governing the free movement of UK and RoI citizens people . Those agreements do not cover the movements of other EU citizens. So I can foresee immigration police at Cairnryan,and any UK airport which takes flights from NI.
You may be prepared to forego your BLT or your BigMac, you may be prepared for your Glaswegian collegues to revert to the appalling diets of high fat foods which caused premature deaths, but not all your countrymen are so noble,and may wish to eat more salads., tasteless as iceberg lettuce and forced tomatoes may be.