I think "nigh-unfalsifiable" is unfair in general when it comes to the use of code words, but I'm not familiar with the facts of the particular case under discussion.
I agree in the general case.
In fact, I fully expect that (for example) an IAT would find stronger associations between "food stamps" and black people than between "epic" and black people, but would not find stronger associations between "food stamps" and white people than between "epic" and white people, and if I did not find that result I would have to seriously rethink my belief that "food stamps" is a dog-whistle in the particular case under discussion; it's not unfalsifiable at all.
But I can't figure ...
Here's the new thread for posting quotes, with the usual rules: