It should rub you the wrong way because the language is wrong! The author has used the wrong word to describe the problem. If you replace the word harm and harmful with difficult it makes sense.

harmful:

of a kind likely to be damaging

difficult:

hard to deal with, manage, or overcome

I've done it for everyone:

>Saturated dark colors against dark backgrounds are hard to read and difficult to parse

>White mentions lack visual clarity and are incredibly difficult for individuals with visual impairment

>Color redesign lacks contrast and are difficult for individuals who are colorblind and/or visually impaired

>Elements lack unity

>Saturated, mid-value colors covering large fields are difficult for end-users

>Text contrast with new colors fail the WCAG test