Responding to students' call for the sacking of John Finnis from Oxford University because of past homophobic writing, I tweeted yesterday that:

If I spend £30,000 on a car I don't expect the salesman to tell me my lifestyle is unacceptable. The idea that universities should be different is a hangover from the days before tuition fees.

This needs expanding. I was not justifying the students' demand but merely getting at a point made by Fred Hirsch back in 1976. He called it the commercialization effect. If we pay for something we have different standards and expectations than we do if we get it for free*. Motivational crowding out happens. If I'm getting something for nothing I'll be more tolerant of any, ahem, idiosyncrasies of its suppliers than I would be if I'm spending a fortune on it. You cannot create a market in something and then be surprised when customers exercise consumer sovereignty. Economic change causes cultural change. The cash nexus might well transform what used to be a learning experience into just another paid-for leisure activity - and people on cruises don't expect to be "challenged" or offended by the waiters,

In this context, what's surprising is just how tolerant students still are: as Will Davies has said, the idea that they are intolerant snowflakes is a figment of the right's imagination. This, though, might not be an immutable fact. It might merely be an example of how culture is slow to change in response to economics. Tuition fees are a sufficiently recent innovation that they have not yet crowded out traditional academic social norms about free enquiry. But they might do so eventually.

In this context, there are many issues to consider. Let's take five.

1. There is, as Aveek Bhattacharya pointed out, a commercial transaction in which people pay to be challenged and even offended - personal training. Isn't this a parallel for university? Perhaps, but the trainer's words of admonishment are a form of roleplay: a trainer who was (improbably) sincerely racist or homophobic wouldn't get much custom. In this sense, there's a distinction between lecturers using thought experiments ("what's wrong with homophobia?") and ones expressing sincere views hostile to some students.

2. Teachers can compartmentalize. The great Andrew Glyn, for example, was never hostile to conservative students despite holding very different political views to them. Perhaps even homophobic teachers can do the same**. The converse is also true here. Lecturers with impeccably PC views in public have not always treated female students as they should: Howard Kirk wasn't entirely a fictional character.

3. The idea that students should be challenged can easily have a class, race or gender bias in practice. Oxford vice-chancellor Louise Richardson has said that "education is not about being comfortable. I'm interested in making you uncomfortable'. But let's face it, it is not white public schoolboys who generally feel most uncomfortable at her institution.

4. There are different ways of challenging students. Instinctively, I'm unhappier with homophobia or racism than I am with challenging political or religious views, because the former attack students' sense of themselves whereas the latter do not or shouldn't: your or religious political beliefs should not be constitutive of your identity in the way your race, sexuality or gender are. But is my instinct correct? Is this distinction tenable? Adam Wagner recently tweeted that he feels "almost physically hurt" when liberal ideas are challenged. That suggests it mightn't be. But this opens a slippery slope I don't like at all: if we're intolerant of racism, why shouldn't we be intolerant too of conservatism?

5. What type of market is that in higher education? Some interlocutors have suggested that if students don't like homophobic lecturers they should leave. This seems silly to me. Education is a bundle of good and bad teachers, so walking out because of one bad egg is impractical, to say nothing of the difficulty of change courses. Voice is a perfectly reasonable alternative to exit.

There are no easy answers here. My point is that in introducing tuition fees, governments threatened to change the very nature of universities. Those who attack "snowflake" students and who assert traditional ideas of academic freedom are guilty of ignoring basic economic realities about motivational crowding out and the commercialization effect. It might be that the strongest, and under-appreciated, argument for abolishing tuition fees is that doing is a way to protect the traditional concept of the university.

* I mean at the point of use. Students have in the past paid for their education out of taxes on their enhanced earnings.

** Finnis is retired: I'm not much interested in his particular case.