What about constant verbal abuse? Or - as in this particular case - the right to bombard (or drown) any useful discussion? Should that be tolerated? I don't know.

For some people this kind of online attacking and lack of freedom to communicate (through effective trolling) may be worse than physical abuse. In the end its the brain interpreting signals and outputting pain.

Your comment is precisely the paradox, though. "You can absolutely tolerant them until they get the majority of votes." First of all, it's not every society where a "majority of votes" grants political power. In Greece, the White Supremacist group (Golden Dawn) holds parliament seats even though they are a small (but vocal and politically active) minority. White supremacists now influence policy in Greece despite being a minority.

In the Middle East, this kind of outsize influence might be even worse. I am no expert on Middle East politics, but I think it's fair to say that the most intolerant factions have striven to gain the most political power, in spite of the political leanings of the mass populations over which they rule.

One issue with intolerant groups is that they tend toward violence and oppression of opposing speech. The tolerant and pacifist among us can allow them to gain enough minority power to effect a political coup, which can result in a societal coup, since having political control can grant you some degree of societal control.

In such a society, espousing tolerance might carry with it the risk of violent retribution (since tolerance is viewed by the "in" group as heresy/dissent). This will cause the intolerance to spread, even if seemingly against the will of more tolerant citizens. In this way, certain ideologies can have a "toxic" societal effect. You don't need to look far in modern history to find examples. And, that's the paradox.

> Or maybe they are, but it consists of running a political party on that platform, encouraging people to vote them in.

> As a society, you can absolutely tolerate them without the use of force, at least until the point where they actually get the majority of votes (but at that point, they are the society, and you're an outgroup in that society).

You just answered your own question

Did I? You seem to be assuming a causal link between suppressing their speech, and them being able to get the majority of votes. I don't see any evidence to this effect - I mean, even just comparing the size of neo-Nazi rallies in Germany (strong hate speech laws) versus US (no hate speech laws), if anything, one would come to the conclusion that the best way to not allow Nazis to come to power through democratic means is to let them freely express their opinions. When you don't, you get the same people running on "anti-immigration" platform and use other dog whistles, which only broadens their base of support.

My opinion is that if there's a real threat of extreme political forces coming to power through democratic means in your society, then that society is already broken, and restricting hate speech is basically just sweeping the shards under the rug and pretending that nothing's wrong.

I have a feeling that that kind of speech, given enough time and tolerance, eventually might escalate to action.

Hate speech is a symptom of a problem, not a cause. Trying to treat a disease by suppressing symptoms is a waste of time at best, and actively harmful at first (because it conceals the progression of that disease, until one day you're violently sick).