Freedom of expression is the most important of all liberties, upon which all other freedoms depend. That’s why it is so troubling when a member of Knesset is punished not for what she has done, but rather for what she has said.The Knesset Ethics Committee will hold a hearing on anti-Israel statements made by Joint List MK Haneen Zoabi in speeches she gave in Berkeley, California, and in an interview with Sue Fishkoff, editor of J. The Jewish News of Northern California.The statements Zoabi said to Fishkoff reportedly included a call to “liberate Americans from the Zionist lobby” and the claim that “anyone who is not anti-Zionist... must recognize their complicity in the tragedy of the Palestinians.”Zoabi also reportedly called to dissolve Israel as a Jewish state and to replace it either with two states – one secular, one Palestinian – or, ideally, one binational secular state with self-determination for both Jews and Palestinians. She said Jews outside Israel had no claim on that land and never did. But Jews inside Israel were a fact on the ground and had rights.Just last month the Knesset Ethics Committee slapped a one-week ban on Zoabi for calling IDF soldiers murderers.Zoabi’s comments are undoubtedly painful for many Israelis to hear. But does this justify punishment? Zoabi defended her comments about IDF soldiers being murderers of Palestinians, saying it was part of her right to free speech to say so, and that she would be happy to provide information about “a large number of cases of murder of Palestinians by soldiers.”In contrast, MKs justified banning Zoabi for her comments about IDF soldiers by claiming that use of the word “murderers” for soldiers acting in the name of the state could not be defended within the framework of freedom of political expression for Knesset members, and that it therefore contravened the legislature’s ethics rules. The Knesset committee ruling is unfortunate.If a similar ruling is made regarding Zoabi’s latest comments it will be another blow to free speech.Limits on freedom of speech have a chilling effect on debate, and this has far-reaching implications.Even the most outlandish claims (such as Holocaust denial, conspiracy claims that Israel carried out the 9/11 attacks, and comparisons of the reality on the West Bank with South African Apartheid) often hide half-truths or are motivated by hidden agendas. Refuting falsehoods or revealing underlying motivations is only possible in an atmosphere of open debate in which all claims are scrutinized.When Holocaust deniers are allowed to speak and are publicly refuted by historical facts backed by eyewitness accounts, documentation and reconstruction of the events, not only are these pernicious ideas more likely to fade away, but more is learned about the Holocaust in the process. The same can be said for conspiracy theories, comparisons between Israel and Apartheid in South Africa, and the statements made by Zoabi.Open debate fosters an intellectual environment in which clear distinctions are made between truth and falsehood. Failure to protect free speech, in contrast, enables an atmosphere in which the line is blurred between truth and falsehood. We have witnessed this happen in Russia where entire political parties were banned from running ahead of the March elections and where vaguely worded laws against “extremist” content have resulted in prosecutions against media outlets and against individual Internet users for daring to mention government corruption, opposition to the war in Ukraine or the annexation of Crimea, support for the LGBTI community or criticism of religion.Obviously, the Knesset’s move to reprimand Zoabi is not comparable to the reality today in Russia. We should be wary, however, of a slippery slope on these matters. Once we outlaw certain types of speech it is impossible to know where restriction of free speech will end.Better to counter Zoabi’s arguments with reason and facts than to punish her for what she says. In the process, not only will Zoabi’s claims be revealed for what they are – hypocrisy and distortion of the facts – the exchange of ideas might also help Zoabi’s detractors better understand their own convictions.