It's free speech that will defeat Islamist preachers in universities I suspect most readers of this blog will agree with Barack Obama's basic point in the video above, which is that by banning racist books and right-wing speakers to 'coddle' oversensitive types, universities are failing students.

This is a problem we have in the UK as well – Brendan O'Neill and Tim Stanley were barred from speaking at a debate about abortion they'd been invited to take part in at Oxford last November, and certain parts of the social justice movement have been waging a quiet war against 'trans-exclusionary' radical feminists (and vice-versa, perhaps) by having them barred from university conferences and events, heckling them when they speak, and so on. People like James Watson have been made untouchable for suggesting that there may be genetic differences in IQ between different races.

This is not entirely a left-wing phenomenon. Today David Cameron has 'named and shamed' universities 'that regularly give platforms to hate preachers who are determined to undermine British values'. It's not clear to me what 'British values' are, or what's so bad about wanting to undermine them. Is belief in the NHS a British value, making free marketeers dangerous too? Is belief in democracy, excluding Jacobite restorationists from campuses and the like?

The obvious response to this is that these people will not just 'undermine British values' but actively encourage students to kill other people. Of course we already have laws against incitement to violence (excessively strict ones, some would say) but perhaps these don't work here. A roundabout suggestion that the, ahem, Zionists are controlling the media and, you know, maybe these ISIS fellas aren't so bad after all is not – and should not be – illegal, but might plant a seed in enough people's minds to lead them to kill.

No doubt there is something rotten in British universities, but I wonder if part of the problem is that opponents of these speakers are heavily restricted by the sort of people Obama attacked yesterday.

How easy is it to oppose Islamism on university campuses? Being anti-abortion is unpopular, but Islamophobia is so forbidden that Ed Miliband proposed to make it a hate crime. Last year Plymouth University's Islamic Society tried to have a speaker from the anti-Islamist Quilliam banned from speaking there. The year before that, a mob of students blocked Israel's deputy Ambassador to Britain from giving a lecture at the University of Essex. There is no shortage of other examples either.

So perhaps institutionalised political correctness is allowing Islamists to get a free pass at universities without being challenged, as it has arguably contributed to child abuse in Rotherham and elsewhere. If feminist comedian Kate Smurthwaite is too edgy to be allowed to perform to Goldsmith University students, what hope do harsh critics of Islamism like Maajid Nawaz or Douglas Murray have?

Banning hate preachers would mean we must also accept the principle of banning Maajid Nawaz for pushing back against them, Tim Stanley for opposing abortion, and Germaine Greer for showing insufficient respect to Caitlin Jenner. It concedes too much.

Open debate is too valuable to give up in places where it is supposed to thrive. It shouldn't be harder for Islamists to speak at universities – it should be easier for their enemies to contradict them. The problem is not what is being said, but what is not being said.