A three-letter word constantly undermines academic freedom and many other freedoms. That word is 'BUT'. We must defend academic freedom BUT 'that freedom comes with responsibilities' BUT 'not for fascist or extremist groups' BUT 'not if it causes offence'.

'BUT' is a key word in the contemporary political lexicon. Those interested in how political freedom is being undermined have to learn how to read it. It means 'NOT' – in the once trendy way of negating a statement – or 'delete all that comes before'. The 'BUTERS' simply don't mean what they say. Try this way of reading the rhetoric in any government policy statement; it works.

Academics For Academic Freedom (AFAF) was founded on the basis that if academics don't draw the line in the sand and defend academic freedom – and freedom of speech – then not only will no one else defend it, but the very idea of freedom is threatened.

This is because academic freedom is the fullest form of freedom of speech and is a beacon for all freedoms. Without the concept of unrestricted freedom of speech all other freedoms are threatened because the very concept of freedom, and a free society, rest on the idea of the unrestricted argument and debate.

But the 'BUTERS' in the academic world dominate academic life and are opposed to academic freedom and freedom of speech. Left-wingers in the University and College Union (UCU) have carried the argument that "academic freedom is cherished BUT with rights comes responsibility. We, therefore, urge universities to act responsibly to protect staff and students and to avoid providing a platform of organisations like the BNP".

UCU would have a point if they meant there were logical consequences to the concept of academic freedom such as having to question everything in the pursuit of truth. However, just linking it to protection and to not giving certain groups a voice is a non sequitur.

These consequences or 'responsibilities' are arbitrarily chosen to weaken the concept of academic freedom and make it a privilege for certain views. UCU should cherish academic freedom as an absolute especially as staff and students too often want to be protected from intellectual views and opinions they dislike.

The National Union of Students (NUS), another 'BUTER', has entirely abandoned free speech and debate in order to 'No Platform' groups and individuals they dislike, starting with 'fascists'. The NUS recognises that this "appears a strange policy for 'democrats' to want, and it does upset some freedom of speech campaigners. BUT fascists hold such detestable and disgusting beliefs, most people feel they cannot bring themselves to have dialogue with them …. The right to free speech brings with it responsibilities, such as not violating others' freedom."

The NUS don't appear to have any idea of what higher education is, or what it means to be a student. The notion that expressing your views at university is being provided with 'platform' shows contempt for the ability of their student membership to make up their own minds about what they hear.

Fortunately, opponents of 'No Platform' are increasingly challenging the nanny NUS. As one student said, when the NUS was trying to persuade East Anglia's students not to oppose 'No Platform' – "You are the fascists going around telling us what we can think".

Universities, with few exceptions, are the worst of the 'BUTERS'. Formally committed to the ever-diminishing right of academic freedom 'within the law', they add so many caveats to it that it ceases to have any meaning. For example, the University of Leeds has a lengthy statement on 'Freedom of Expression' that, after two statements about academic freedom as an ideal and in law, adds the BUT that "This does not mean… that the right to freedom of expression is unfettered".

The limitations the institution adds are lengthy and include the need to "protect national security and public safety"; to "prevent disorder or crime"; to "protect the reputation or rights of others"; to "prevent the disclosure of information received in confidence"; to "promote good relation between persons of different racial groups"; to "be set in the context of the University's values" and not to "give rise to an environment in which people will experience – or could reasonably fear – harassment, intimidation, verbal abuse or violence because of their ethnicity, race, religion and belief, sexuality, gender, disability or age".

The penultimate limitation by Leeds comes from Universities UK's advice that "if an expression of views is highly offensive with the potential of developing into harassment, or may constitute criminal activity, the balance is likely to be in favour of restricting that activity" (my italics).

Most interesting views are highly offensive to some people or groups and the 'buters' cry of 'offensive' is the way of silencing freedom of expression in our culture of easy vulnerability. The statement is a model for universities who want academic freedom BUT.

Bill Rammell, the Minister of State for lifelong learning, further and higher education, in a speech last November, put forward a welcome defence of academic freedom and made clear his opposition to 'No Platform' policies and to 'academic boycotts'.

He put the civic consequences of academic freedom clearly: "If our students learn to respect the right to disagree and the right of some else to disagree with them universities will have played an important role in embedding our core values in the rising generation, thus preserving them for the future".

There is much that anyone would welcome in his speech, then comes the BUT: "Academics and students alike must be free to go where their intellects lead … BUT at the same time they are not separate from society. The privilege of academic freedom, the privilege of power to shape young minds, also brings grave responsibility".

Academic freedom for Rammell has an instrumental purpose to defeat the extremist threat to society by ensuring that by arguing with those who propose extreme views that we "let their views be exposed and challenged for the falsehoods they are".

It is tempting to argue that all rational people will agree about core values and oppose extremism but in the Socratic tradition, academics must use their academic freedom to put those 'core values' to the test. Academic freedom cannot be 'balanced' by required outcomes however welcome and comforting they may be.

If the unions, universities and the universities department really believe that academic freedom is a value, they should simply uphold it as the responsibility to speak your mind and challenge conventional wisdom. No BUTS.