I think today even faux pas is a bit of a stretch. The same way wingtip shoes have made their way into modern business attire, so have button-down collared shirts (at least in the United States and probably Canada). While they may not be considered as elegant or classy as pointed-collar or spread-collar shirts, I am of the opinion that they no longer fall under the category of "wrong". Clothing styles and fashion are ever-changing and ever-evolving, which is one reason it is often hard to nail down "traditional". Some men, perhaps not a majority or even in great numbers, have been wearing button-down collars with suits since at least the 1930s.