When the Civil Right Act and Americans with Disabilities Act were created, people asked the government to enforces these acts. Whatever you think of merits of DEI, the government decided to create DEI in order to enforce the Civil Rights Act and Americans with Disabilities act.
The problem is because they decided that DEI would be the mechanism to do this with, once DEI is rescinded the question is: If you're not going to enforce the Civil Right Act and Americans with Disabilities Act through DEI, which mechanism do you plan to use to enforce them? According to this take, once DEI is rescinded there is no mechanism to enforce the Civil Right Act and Americans with Disabilities Act anymore.
I'm pretty sure that most leftwing and rightwing people will agree that out of 3 millions government workers it's not entirely unlikely that there would be some some valid cases of discrimination against minorities and those with disabilities. The claim is that, whether DEI sucks or not, there is no avenue to contest racism and discrimination in government hiring anymore.