"Nobody supports complete freedom of speech"

That's the line that always gets thrown back at libertarians or indeed anyone defending the right to print cartoons that offend some people.  That lack of absolutism in freedom of speech is seen as justification for any exception that anyone wants to claim, which of course means the "right" doesn't exist.

However, the argument that there is no absolute unrestricted right to free speech and so free speech is "up for grabs" is from the same school of thought as those who claim you can't have absolute freedom or anyone can do violence to anyone else.

It's missing the point that the issue is around individual rights, and that restrictions on free speech are not restrictions on individual rights, but the boundaries between individual rights.  It is the same as my right to use my body as I wish, as long as I do not deny that same right to others.  Otherwise I am not asserting an individual right that all people have, but asserting privilege to do as I wish to others that I am not extending to others.

The same applies to the boundaries of free speech.

So what are these boundaries from a libertarian perspective?

No right to use platforms or property owned by others:   You can say, write or produce media if you wish, but you have no right to demand others provide you a platform to do so.  You do not have a right to demand a newspaper print your article, nor do you have a right to be on someone's private property and do as you wish against the wishes of the property owner.  The quid pro quo is that neither does anyone have a right to demand you print their articles, or be on your property and say or distribute content that you disapprove of.   Say what you wish on your own property, say what you wish on your own platform (and bear in mind this means there are no restrictions on who can publish, broadcast or produce content or talk), or as is often the case, obey the rules of someone else's platform.  This also includes accepting the rules of property that you enter.  When you enter a cinema, the classic shouting "fire" is likely to be a rule that would get you ejected from the premises, but also subject you to a lawsuit for the harm done to the owner and the others who acted on the false call.   Free speech, as with all actions are constrained by property rights. 

No right to use the intellectual property of others, without their permission:   Copyright and patents are the cornerstone of many industries and careers.  Those who apply their minds to pens, computers, paintbrushes, musical instruments and even their voices, have the right to own what they produce and to sell the proceeds of the products of their minds.  It is hardly a restriction on your own speech to simply reproduce that of another, if the other's speech is not restricted.

Defamation is about property rights too: Whilst less material, one's reputation is still something that belongs to you and has value, as it affects employment, business and personal relationships.  If someone distributes content that is demonstrably false which seriously diminishes your reputation (i.e. claims of criminal conduct), then there is a right to not only respond with free speech, but to claim financial damages for the harm done.  This does not prohibit such speech, but means that the damage done due to such speech can be claimed.

Censorship of recordings of crimes against the person:  There is no justification for restricting written, drawn, painted or virtual depictions of any events, as this is a creative endeavour that involve no person other than the creator/producer.  By contrast deliberate video, still or audio recordings of actual violent or sexual crimes being committed (recording made with the knowledge the crime would be committed, rather than security cameras incidentally recording the commission of a crime), are a part of the actual offence, as the person who made the recording is an accessory to it.  In such cases, such recordings should be the property of the victim, and can be used as evidence of the original crime, or treated as the victim wishes.  If the victim is not identified, the recordings are evidence of a crime and should be treated as such, until the victim is identified and can specify the fate of the recording.  This is how so-called "snuff" films, child pornography and recordings of actual rapes should be treated, as they are extensions of the actual crime.  Recordings of any other legal behaviour, regardless of it being sexually explicit, including simulated crimes, are different, as these are not crimes.  Recordings of acts without the consent of those involved could be considered violations of property rights (if the recording is undertaken without the consent of the owner or person with licence to occupy the property from the owner) or, if the other party or parties are aware of the recording, as void consent (consent obtained under objectively fraudulent circumstances). 

Prohibitions against threats are an extension of the crimes that are being threatened:  A threat to commit a crime against another is a crime, it is the possible step before the attempt to commit a crime.  The threat is itself an initiation of force, as it may result in the victim responding in submission to the threat.   In this case the speech is an initiation of force that denies the right of the recipient to live in peace.  This does not change if it is a group of individuals making threats to a single or a group of individuals, in other words it covers true hate speech, being the use of speech to threaten violence.

Fraud:  You can make statements that are false, or false claims, or lie about the contract that you are making with another party, but all of these can be subject to criminal and/or civil action for fraud.  This is, in effect, another form of initiating force, for it leads people to enter into contracts, exchanging value, on the basis of a lie, so that value is not exchanged on the basis upon which it was originally agreed. 

In all of these cases of limitations on free speech, the limitation is a demarcation of the boundaries between  the same rights held by all individuals concerned, whether they be property rights or the right to decide what one does with one's own body (recording violations or obtaining consent fraudulently being the violations).  They are not limitations based on a party being offended or in some statist definition of protecting public morals.

So no, those of us who argue for unrestricted free speech are not hypocrites when these limitations which are consistent with individual rights are quoted as the boundaries to free speech.  That is why those arguing for free speech, but also supporting "hate speech" laws fall victim to the claims by Islamists that insulting "the prophet" is "hate speech" because Islamists consider "insulting  the prophet" to be a greater offence than "hate speech" towards Muslims.

Do those of us arguing for free speech say everyone should be offensive to everyone else? No.  It is neither rational nor intelligent nor even ethical to be a whimsical vulgarian, but if it does not infringe upon the rights of others, then it is not the role of the state to use force to control it.

Within this is the right to insult any philosophy, whether based on religion or based on a this-wordly set of beliefs, regardless of how rational or whimsical they are.  It includes the right to insult any art, any speech, any person, and to praise as well.  Yes, it means that frequently you'll be offended, as will I, probably about different things, different words, images or sounds.   

However, it is only through free speech that human beings can learn from each other, can apply their minds to the full evidence of expressions from each other and respond accordingly, with speech or actions.  The right to free speech is the most fundamental egalitarian right that there is, for it is a statement that no power has the right to use force to close your voice, no power knows better than you as to what words, sounds, images and objects you can see and interpret and the sole limit on this is when your production or consumption of speech violates another.