But my rule is that if I am not wearing anything other than a bra under my article of clothing, that article of clothing isn't coming off to walk through a WTMD.

I don't wear bulky clothing whilst travelling, and I don't wear sweatshirts. I usually wear a light weight top, or a light weight sweater, or the more complex 'cardigan'. That I will remove if ordered (which is usually only in America) as I am usually wearing a light tshirt underneath.

But nobody should have to remove an article of clothing if it is all that they are wearing ie with nothing underneath, just to walk through a metal detector.