It's kind of the paradox of democracy -- how do you square the rights of a free society against those would use those rights to advocate against them or overthrow them?
The first step is to accept that it is a paradox, that no solution is going to be perfect and you're not going to fix everything. Politely ignore anybody who speaks in absolute terms or comes up with trite little not-even-wrong aphorisms like "you have the freedom to do anything you want except the freedom to take away freedom from others".
Then, before imposing any laws, you have to remember that the acid test is not how they will be interpreted by judges and juries, but how it will be interpreted by publishers, employers, landlords, public institutions, police, security guards etc. who will tend to interpret them in the broadest, most restrictive possible way to cover their own backs.
Everything is a risk/benefit tradeoff - and the risk can never be zero.
In the case of freedom of speech, though, it's possible to be almost absolutist if you insist that any activity you do want to control (harassment, incitement to violence, etc.) must involve actions or behaviours that go beyond the words that are said or published. So, if you want to prosecute someone you should not simply have to prove that they uttered the word "fire" in a public theatre, but show evidence that they intentionally set out to cause disruption*. You can prohibit "inciting violence" if you like, but it needs to be absolutely literal, or supported by other activities. Harassment should need to include a pattern of behaviour that shows victimisation. Once you start banning speech that might induce panic, could be interpreted as inciting violence or that made the victim feel harassed the slippery slope beckons.
Unfortunately, both religious extremists and politicians do like to pretend that they have the solution to everything, while lawyers lurk to apply 20:20 hindsight to anybody who takes a risk and loses, and lawmakers who seem to think that if a legal decision misinterpreting their law is put right on the third appeal then everything is rosy.
(* Of course, although this is a popular example, they're quite rightly going to that special hell reserved for people who talk at the theatre *anyway* so free speech isn't really relevant)