When Zakir Naik, the Islamist hate preacher, was banned from Britain, right-wingers didn’t pack the streets to protest.  And now that a ban on Donald Trump has been floated, left-wingers aren’t marching in defence of his right to free speech.

Which is evidence that most of us are less committed to it than many of us claim to be.  Is there, then, a defensible rationale for barring the former – which this site urged at the time – but not banning the latter?  Theresa May would say that the Home Office should have the power to ban foreigners from Britain if they are likely to incite or provoke violence.  One can counter-claim that it shouldn’t have the right to do so, or that the authorities should wait until the person in question has actually committed an act of incitement.  However, it is at least arguable that the presence in the country of some visitors, amplified and projected by media coverage, can itself do the job before any words are spoken at all – that a person can be, as it were, a walking, talking, living incitement.

It is not necessary to support May’s proposed Extremism Disruption Orders – about which ConservativeHome is very doubtful indeed – to believe that this case has a point.  Context is everything.  Islamist extremism is at war with liberal democracy, and indeed mainstream Muslims, both culturally and literally.  And one of the ways it wages that fight is to curtail the free expression without which a University, for example, cannot thrive and without which its students cannot flourish.  So it is that extreme Islamism on campus on menaces Jewish students, gay students, Muslim students who aren’t signed up to its tenets, and so on.  University Vice-Chancellors would fall over themselves to bar neo-nazi speakers from their institutions.  They should treat Islamist fascists, as Hillary Benn calls them, in the same way.

The question is not just an academic one, in either sense.  Extremist Islamists are a threat to life and limb in Britain.  Neo-nazis are, too: one of them, David Copeland, murdered three people and injured about 70 in the Admiral Duncan pub bombing of 1999.  May was thus right to bar Matthew Heimbach, an American fascist, only a few weeks ago.  None the less, people have been banned from Britain who have nothing to do with Islamist or neo-nazi extremism at all.  Consider the case of Tyler the Creator, the American rapper: he was barred because of lyrics considered offensive.  (These have apparently “heavily featured anti-gay rhetorics and lyrics about rape”).  Did this ban fall on the wrong side of the line?  For what it’s worth, our view is that it did.  Without free expression, the state becomes too powerful and a society becomes infantilised – and, in any event, barring people can sometimes be counter-productive.

So one comes back, once again, to that crucial matter of context – or circumstances, as Burke would have put it.  Would a visit to the House of Lords by Geert Wilders have been a threat to public order?  This site thinks not.  Would that of Robert Spencer and Pamela Geller to an English Defence League rally?  May had good reason to think so.

What about Trump?  Ministers are falling over themselves to say that the question is academic: he has no plans to come here.  But were he to seek to do so, all that can be said is that the presumption must always be in favour of free speech.  It should not be over-riding – which takes one back to the point about Islamist or neo-nazi extremists.  But it should always endure.

Perhaps the best response to Trump’s  attempt to bolster his vulnerable position in the Republic presidential race came from the admirable Sayeed Kamall.  “Hi ,” he tweeted. ” You’re welcome to visit & I’ll show you around. No need to return the invite, especially as you won’t let me in.”