The ad did not call the 40,000 people Chinese. Trump’s administration has been attempting to paint its ban on travel from China as proof of them taking the coronavirus seriously. Biden’s campaign is poking holes in that argument. I really don’t see a problem with the ad here. You could probably say “China” instead of “Chinese” in several places, but I really don’t buy that it would satisfy those who are upset by the ad, nor do I think a racist would be less of one if you referred to the nation or party instead of a demonym.