This is a very confused set of remarks. I rather hope he lost the debate.

For one thing, neither the Tim Hunt nor the Justine Sacco cases have anything to do with "national security", unless Frum is further going to argue that the government has an interest in preventing the act of saying stupid things from having consequences. There was not even anything criminal involved. The Le Pen and Essex University events, while I don't particularly care for efforts to prevent someone from speaking, were rather in the nature of the whole freedom-of-speech thing. Protests do happen. And when he goes on to wonder "if British thinkers, writers, and artists dread economic reprisal," I feel compelled to point out that he's gone completely off the rails: if

"We are gathered here today to discuss the state of liberty in the United Kingdom—and the purported threat to those liberties from measures to promote the nation’s security, especially against terrorism."

then the majority of his comments aren't even in the same county, much less the building holding the debate.

Now, he does manage to touch on the actual topic when he says, "And if we consider other liberties also cherished by free people—[...] the right of a nation’s citizens to be free of punishment by their nation except in accordance with positive law applied with due process [...]" but he consistently fails to actually make any argument on that topic. Well, sort of. Unfortunately, "they do it, too, and worse" is not really compelling.

Now, I do get his side points. I was a system administrator for many years, and if you want an example of a job that is only noticed when you dramatically screw up, it is a fine one. And I'm not one to think that "security" and "liberty" are in eternal and unforgiving opposition: I also get that meaningful liberty is impossible without a solid base of security. (I also get that Frum would disagree strongly with me about the details; given his little attacks on anti-discrimination and environmental protection, we might have a problem over the definition of the liberty to employ and to be employed or the right to enjoy property.)

But I'm afraid Frum doesn't get that, in a free society, the answer to Abraham Lincoln’s famous question: “Must I shoot a simple-minded soldier boy who deserts—while I must not touch a hair of the wily agitator who induces him to desert?” is a pretty solid "Yup." Perhaps followed by "Them's the risks if you don't want to be the target yourself." You certainly can't yell "Fire!" unnecessarily in a crowded theater, but if you're as confused about the difference between a military threat, a criminal threat, a social or economic threat, and perfectly legitimate disagreement as Frum, it's entirely too easy and tempting to declare "Packing too many people into a single room is bad" as a threat requiring a military response. Been down that road before, in fact.

If you don't buy that, consider the "Prevent" program he describes as "an effort worth applauding". The linked article mentions,

"But one of the biggest knocks to Prevent came when it emerged four years ago that CCTV cameras in Muslim areas of Birmingham - 72 of them hidden - were partly funded by Home Office counter-terrorism cash.

"The loss of confidence and trust in police was enormous."

It shouldn't be a wild surprise that

"Mr Khan said: 'Most young people are seeing [Prevent] as a target on them and the institutions they associate with.'"

And that is what is hard to reconcile with "the right of a nation’s citizens to be free of punishment by their nation except in accordance with positive law applied with due process".