In his drive to purge diversity efforts in the federal government and beyond, President Trump has expressed outright hostility to civil rights protections.

He ordered federal agencies to abandon some of the core tenets of the Civil Rights Act of 1964, on the basis that they represented a “pernicious” attempt to make decisions based on diversity rather than merit.

But in recent weeks, Mr. Trump has turned to those same measures — not to help groups that have historically been discriminated against, but to remedy what he sees as the disenfranchisement of white men.

The pattern fits into a broader trend in the administration, as Trump officials pick and choose which civil rights protections they want to enforce, and for whom. Across the government, agencies that have historically worked to fight discrimination against Black people, women and other groups have pivoted to investigating institutions accused of favoring them.

“The plain message that they are conveying is: If you even think about, talk about or claim to be in favor of diversity, of equity, of inclusion, of accessibility, you will be targeted,” said Maya Wiley, the president and chief executive of the Leadership Conference on Civil and Human Rights.

“They’re conveying that white men are the most discriminated against people in American society,” she added, “and therefore entitled to affirmative action.”