Set aside your political bone to pick for a few seconds and think about it. The author isn't "blaming" anything on diversity.

Diversity is just the "thing of the minute" in the context in which the author is writing about. In the 1950s he could write the same article and substitute in anticommunism. The "thing of the minute" will probably always be some broadly appealing subset of the culture and politics of the society and time in which the organization exits. It doesn't matter what the virtue everyone is professing is. What matters is that the virtue is at best ancillary to whatever the organization's goals are and resources directed at it are resources not directed at keeping the business running and prepared for the future.