It's really too bad you were in an airport, because that's one place you don't want to make a scene. I can understand people mistaking tartans, even ones that don't look anything alike, but it doesn't give them the right to be condescending. If you had been anywhere well this lady was deserving of a in-your-face tartan lesson.

And to say your accent was fake; even in the airport I would've whipped out my passport on shown her that she was so very wrong.

You handled the situation very well. Just for that, you get a and a