Why Does Israel Allow a Seditious Man To Serve ... in the Knesset?

If the "Kach" or "Kahane Chai" parties are considered by the state of Israel to be “far right,” “terrorist,” "a danger to the state," and are barred from the Knesset, then why is Ibrahim Sarsur of the"Ra'am-Ta'al" party allowed to keep his seat?

Ra'am Ta'al is a seditious Arab political party that spouts more rhetoric then any other extremist group in Israel, however they are left unfettered by the Knesset since Arab Islamist parties are considered viable political parties in the country. Ibrahim Sarsur is an Israeli Arab politician and Knesset member, and is currently leader of the United Arab List. In April 2008 he stirred controversy when, following an Israeli air strike in the Gaza Strip which killed a woman and her four children, he compared the actions of Israel to those of the Nazis:

Israel's killing of innocent people is reminiscent of some very dark times, including that of the Nazis.

This proved to be the least controversial thing to come from his mouth lately. The Walid Shoebat Foundation has uncovered damning evidence in a video that what Sarsur says in English to a Western audience is far different from what he says in Arabic to his Arab constituents.

Sarsur, speaking in Arabic at Abdul Rahman’s club in Israel, openly praised Hezbollah for "defeating Israel." He also said he awaits seeing Hezbollah's planners and strategists (whom he claims have a local presence) repeat their victory against his enemy Israel during the 2006 fiasco in Southern Lebanon:

There is a force in Southern Lebanon that proudly raised its head to challenge American and Israeli supremacy with a project that carries the seeds of dignity and is based on Islamic pillars and foundations and has a vision to manage the war with the enemy [Israel].

Its internal management is well designed to benefit the Umma [Islamic nation]. Then came the blow that ended in the humiliation through these fighters grinding the nose in the dirt of the number one power in the Middle East, that is Israel. This defeat caused an earthquake measured ten on the Richter scale and on the political scale in Israel. The aftershocks continue from this great earthquake of 2006 until today.

There was none left [without humiliation] from the Defense Minister, Interior Minister and Prime Minister. ... Keep in mind, there is strength and strategic insight and presence locally and regionally for Hezbullah beginning in 2006 'til today. They are thinking on how to return this fear to Israel and how to destroy Israel's deterrence which is the pillar of Israel's continuation and if this happens -- this means that the line will begin to point extremely downwards for Israel’s deterrence.