Without getting into the essential argument, Robinson is correct that, whether right or wrong, journalists have essentially agreed the issue is off the table.
Robinson hints that by avoiding the topic, journalists aren't doing their job. But if I may posit a theory, it occurs to me that much of the coverage of a GOP Primary is done by conservative writers and pundits. And after forty years of being accused of bigotry, most conservatives -- including writers -- are deathly afraid of being accused of such a sin. As such, they go out of their way to avoid being accused of such behavior, and as a result, avoid the question like the plague.