Not a whole can of worms at all. It's national pride, it isn't a case that it just displays the english flag incorrectly, but the irish and the scottish as well.
In the end all you need to say is "Thanks SMARTY for pointing that out and we'll get it rectified".
People have fought and died under that flag, they lost thier lives for this country and that flag is the banner for which they fought, complacency towards it is disrespect towards those that have fought and served this country and in some cases lost thier lives.
There are a number of ex and serving servicemen and women on this forum and they have respect for the Union Flag / Jack (for our naval people), to show disrespect, even if unintended, is offensive to those that served as much as anything else.