At the very least, these candidates do a disservice to the American people when they are clearly wrong about the Constitution. But beyond their miseducating the public, the substance of their comments is truly frightening. They apparently reject the very notion of judicial independence.
They also seem to reject the idea of the rule of law and the need for judicial review to enforce the Constitution. In Marbury, the Supreme Court also explained that the limits of the Constitution are meaningless unless there is a judiciary to enforce it.
Perhaps these attacks on the federal judiciary are just part of the exceptionally poisonous rhetoric of these divisive times. But it is scary to think of the possibility of a president who largely rejects judicial review, gives no apparent importance to judicial independence, pledges to defy Supreme Court rulings or wants to remove federal judges based on disagreement with their rulings. And yet these are changes that candidate after candidate in the Republican race has been talking about.