I think a lot of people don't like DEI because they don't agree with the underlying premises. For example, DEI says there is a history of structural discrimination in higher education, that teachers must be aware that these biases exist, and that teachers must work to counter these biases. Diversity statements during hiring exist to see how well candidates understand those issues and have worked to improve the situation.

Some people do not like DEI because they want to believe they are in a meritocracy, and they are a professor simply because of personal effort.

Problem is, there's a lot of evidence supporting that DEI premise, and demonstrating the flaws in the meritocracy viewpoint.

Some do not like DEI because they believe accepting the systemic racism premise means accepting that most people are racist, while the evidence is that a system built on racism can continue to be racist even if no one involved is racist. We have generations to go before the wealth inequalities caused by deliberate racist government policies disappear. We have drug laws on the books which were created to persecute blacks more than whites. We have place names and statues meant to honor and remind everyone of white supremacists. These laws and statues were created by long dead racists and still enforced by non-racists.

There's an old quote: “If you have the law, hammer the law. If you have the facts, hammer the facts. If you have neither the law nor the facts, hammer the table”. https://quoteinvestigator.com/2010/07/04/legal-adage/

Since the premise is against the professor, instead attack the requirement to have a diversity statement. Liken it to Orwellian thoughtcrime and Soviet apparatchiks and anything else that might sound bad. It just has to have enough emotional power to get people riled up - it does not have have to be part of a larger, logically consistent framework.

Compare diversity statements to 1950s loyalty oaths, since those sound bad. It doesn't matter that 100,000s of people, including university professors are still required to sign loyalty oaths to get their job, because the point isn't to get rid of loyalty oaths, the point is to figure out some way to not sign a diversity statement.

Don't try to explain why some loyalty oaths are acceptable while others are not, because that's hard. Instead, just say that a political test is bad, and be "suspicious of an institutional requirement to do public good" .. while conveniently omitting how government funded higher education exists because of politics and how universities for centuries have said they contribute to the public good.

And even though this a diversity statement isn't actually oath, ignore how all sorts of other things are likened to loyalty oaths, like the Musk/Twitter example I gave earlier or even how the Pony Express riders swore an oath for their job.

Hammer the table and don't get caught in the weeds.