Who is competent to decide what offends?

The following statements are included:

“You speak good English.”

“When I look at you I don’t see color.”

“America is a melting pot.”

“America is the land of opportunity.”

“Everyone can succeed in this society if they work hard enough.”

How long until people start deeming the phrase "America is a country" as a cultural and racial micro-aggression? I'm happy the author calls bullshit on people trying to say "XYZ is offensive to those people!", but the author still seems to support micro-aggression training if they get "better sources" on trigger words.

What if I'm offended by the answer?

A sound approach to teaching “cultural competence” might inform by exploring the history of blackface; or why Sikhs carry a small knife; or common challenges that orthodox Christian students experience on secular campuses; or the historical experience of a Native tribe with many members enrolled; or differences in classroom culture that Chinese exchange students might exhibit; or the hijab’s meaning. Such particulars would best be shaped by the composition of the student body at a given institution.

But when training faculty members or educating students so that they are “culturally competent,” a process that should involve telling them pertinent facts, is instead used as a pretext to indoctrinate them into a contested ideology, the laudable becomes objectionable.