DEI seems to have taken over from Woke as the all-purpose MAGA terms for “this is bad”. DEI stands for diversity, equity, and inclusion. As with Woke, which seems to an accusation of using rational thought, DEI seems like it would be difficult to interpret as bad. Saying that you strongly oppose diversity, equity, and inclusion is a pretty frank admission of your values.
This use of DEI seems to translate directly as “insufficiently racist”.
Don’t use the acronyms when they use it. Ask them why the particular parts bother them so much. Call out the bigotry and make them express it without any safety of inventing a bad word that avoids an argument.
Hell, I bet have of the people against DEI don’t even know what it stands for.