As someone below commented, Jackson’s comments basically parallel the argument of every anti-immigrant white person. “They come here to take our jobs.” “They’re willing to work for less.” “They’re not ‘real’ Americans.” It doesn’t appear that he made the “they drive down wages” argument, but it wouldn’t have shocked me. It’s pretty obvious that this is a tendency that isn’t related so much to any specific group, but to a sense of scarcity and in-group thinking.
I will say though, that I read an article that basically made similar arguments about British actors in general without the racial angle (though authenticity wasn’t considered an issue). If I recall correctly, they made similar arguments about superior training in Britain. It wouldn’t surprise me if it’s the case, as impolitic as it might sound.
I don’t know, I guess there could be some unconscious bias at work here, but I’m more inclined to trust DuVernay’s and Peele’s judgment that they were simply better for the part than to presume they were under the sway of preconceptions or that Jackson’s pretty predictably protectionist attitude.