Of course we all know the answer to this seemingly incomprehensible paradox. It is the FEAR of being labelled a racist, a fear as dread as that of being labelled a heretic in an earlier period when truth was also no defence against the dogma of religious correctness.
With the benefit of hindsight, we know how invidious that fear was both for science and society. And we rightly consider that period to have been an era of darkness and tyranny in which countless "heretics" suffered cruelly at the hands of the inquisitors whose mission then (now) was to "root out heresy (racism) in all its forms, wherever and whenever it appears".
So on the side of darkness and ignorance are "racists" who question or deny the holy scriptures of the god of equality.
Against them are the forces of light and goodness, so-called "liberals" who heartily promote freedom of expression provided they endorse what is being expressed. The holy warriors for the cause are the "anti-racists" latter-day inquisitors - self-righteous thugs on their mission to "root out racism in all its forms wherever and whenever it appears".
"It is difficult to get a man to understand something when his salary depends upon his not understanding it."