Please, give me some credit. Who assumes that any nation's population, or any sufficiently large group of people, really, is a homogeneous, uniform, or monolithic in their opinions? I certainly don't.
Sure, but the point is that a wide spectrum of people, particularly on the left, believed so strongly that WTO was such a net negative for the average American they were willing to violently riot over it.
So when we talk about “a useful tool” in the American toolbox, we should keep in mind that tool mostly, or at least has the perception, of benefiting only the rich.