NEW HAVEN, CONNECTICUT –

Here's what's scariest about the last week's incident at Middlebury College in Connecticut, where protesters shouted down the social scientist Charles Murray and injured a professor who was escorting him from the venue: It felt like an everyday event. So common has such odious behavior become that it's tempting to greet it with a shrug.

According to the Foundation for Individual Rights in Education, 2016 saw a record number of efforts to keep controversial speakers from being heard on campus — and that's just in the United States. To be sure, not all of the attempts succeeded, and the number catalogued, 42, is but a small fraction of the many outsiders who give addresses at colleges and universities each year. The real number of rejected speakers is certainly much higher, once we add in all the people not invited in the first place because some member of this or that committee objects to their views, or because campus authorities fear trouble. But even one would be too many.

I could write a paean to the vital importance of dialogue, both on campus and in a democracy, but I have done that before, sometimes at considerable length. I could remind the loud and increasingly violent mobs of campus censors that the university should be treated as a space where even outrageous ideas are treated with respect, and the mode of opposition is rational dialogue. I could warn them that their fits are increasing the chances of President Donald Trump's re-election. Or that people not blessed with the opportunity to attend an elite college might begin lining up behind Trump's impish suggestion after the Berkeley riot that campuses where invited speakers are turned away be denied federal funds. And I might point to the risk that states will adopt such rules as the Campus Free Speech Act, allowing someone whose speech was restricted to sue colleges and universities for damages.