For someone who complains about a post-truth society and citing studies you won't read, you could possibly consider reading the paper yourself.
Both the APA article and the PDF you are quoting from refer to Sue's article on microaggression. Sue's
2007 paper, by itself, did not actually research if microaggressions are an issue--the abstract itself refers to the paper as a taxonomy. I.e. the purpose of the paper was to introduce, define, and illustrate terminology and ideas for future research projects.
I'd be very interested in seeing what studies have been done since 2007 that document microaggressions impact. A quick read-over of the
wikipedia's effect tab, however, suggests nothing has outright disproved the theory but the field hasn't exactly found its "silver bullet" study either. If there's a particular study I should be focusing on, however, I'm all ears!